Projection optical system, exposure apparatus, and exposure method

ABSTRACT

A projection objective includes at least four curved mirrors, which include a first curved mirror that is a most optically forward mirror and a second curved mirror that is a second most optically forward mirror, as defined along a light path. In addition, an intermediate lens element is disposed physically between the first and second mirrors, the intermediate lens element being a single pass type lens. The objective forms an image with a numerical aperture of at least substantially 1.0 in immersion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. patent application Ser. No. 11/882,208filed Jul. 31, 2007, which is a continuation of U.S. patent applicationSer. No. 11/266,288 filed Nov. 4, 2005, which in turn is acontinuation-in-part of International Application No. PCT/JP2004/006417filed May 6, 2004. Application Ser. No. 11/266,288 also claims thebenefit of U.S. Provisional Application No. 60/721,582 filed Sep. 29,2005. The disclosures of these prior applications are incorporatedherein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to a catadioptric projection opticalsystem, exposure apparatus, and exposure method and, more particularly,to a high-resolution catadioptric projection optical system suitable forexposure apparatus used in production of semiconductor devices,liquid-crystal display devices, etc. by photolithography.

RELATED BACKGROUND ART

The photolithography for production of the semiconductor devices andothers is implemented using a projection exposure apparatus forprojecting a pattern image of a mask (or a reticle) through a projectionoptical system onto a wafer (or a glass plate or the like) coated with aphotoresist or the like. The resolving power (resolution) required forthe projection optical system of the projection exposure apparatus isbecoming increasingly higher and higher with increase in integrationdegree of the semiconductor devices and others.

As a result, in order to satisfy the requirements for the resolvingpower of the projection optical system, it is necessary to shorten thewavelength λ of illumination light (exposure light) and to increase theimage-side numerical aperture NA of the projection optical system.Specifically, the resolution of the projection optical system isexpressed by k·λ/NA (where k is the process coefficient). The image-sidenumerical aperture NA is represented by n·sin θ, where n is a refractiveindex of a medium (normally, gas such as air) between the projectionoptical system and the image plane and θ a maximum angle of incidence tothe image plane.

In this case, if the maximum incidence angle θ is increased in order toincrease the numerical aperture NA, it will result in increasing theinput angle to the image plane and the output angle from the projectionoptical system, so as to increase reflection loss on optical surfacesand thus fail to secure a large effective image-side numerical aperture.For this reason, there is the known technology of increasing thenumerical aperture NA by filling a medium like a liquid with a highrefractive index in the optical path between the projection opticalsystem and the image plane.

However, application of this technology to the ordinary dioptricprojection optical systems caused such disadvantages that it wasdifficult to well correct for chromatic aberration and to satisfy thePetzval's condition to well correct for curvature of field, and that anincrease in the scale of the optical system was inevitable. In addition,there was another disadvantage that it was difficult to secure a largeeffective image-side numerical aperture while well suppressing thereflection loss on optical surfaces.

SUMMARY OF THE INVENTION

A first object of the embodiment is to provide a relatively compactprojection optical system having excellent imaging performance as wellcorrected for various aberrations, such as chromatic aberration andcurvature of field, and being capable of securing a large effectiveimage-side numerical aperture while well suppressing the reflection losson optical surfaces.

In the case where the projection optical system is composed of onlyreflecting optical members and in the case where the projection opticalsystem is composed of a combination of refracting optical members withreflecting optical members, with increase in the numerical aperture, itbecomes more difficult to implement optical path separation between abeam entering a reflecting optical member and a beam reflected by thereflecting optical member and it is infeasible to avoid an increase inthe scale of the reflecting optical member, i.e., an increase in thescale of the projection optical system.

In order to achieve simplification of production and simplification ofmutual adjustment of optical members, it is desirable to construct acatadioptric projection optical system of a single optical axis; in thiscase, with increase in the numerical aperture, it also becomes moredifficult to achieve the optical path separation between the beamentering the reflecting optical member and the beam reflected by thereflecting optical member, and the projection optical system increasesits scale.

A second object of the embodiment is to achieve a large numericalaperture, without increase in the scale of optical members forming acatadioptric projection optical system.

A third object of the embodiment is to provide an exposure apparatus andexposure method capable of performing an exposure to transcribe a finepattern with high accuracy through a projection optical system havingexcellent imaging performance and having a large effective image-sidenumerical aperture and therefore a high resolution. In order to achievethe above-described first object, a projection optical system accordingto a first aspect of the embodiment is a catadioptric projection opticalsystem for forming a reduced image of a first surface on a secondsurface,

the projection optical system comprising at least two reflectingmirrors, and a boundary lens whose surface on the first surface side hasa positive refracting power,

wherein, where a refractive index of an atmosphere in an optical path ofthe projection optical system is 1, an optical path between the boundarylens and the second surface is filled with a medium having a refractiveindex larger than 1.1,

wherein every transmitting member and every reflecting member with arefracting power constituting the projection optical system are arrangedalong a single optical axis, and

the projection optical system having an effective imaging area of apredetermined shape not including the optical axis.

In order to achieve the above-described second object, a projectionoptical system according to a second aspect of the embodiment is acatadioptric projection optical system for forming an image of a firstsurface on a second surface, the projection optical system comprising:

a first imaging optical system comprising two mirrors, for forming anintermediate image of the first surface; and

a second imaging optical system for forming the intermediate image onthe second surface,

wherein the second imaging optical system comprises the followingcomponents in order of passage of a ray from the intermediate imageside:

a first field mirror of a concave shape;

a second field mirror;

a first lens unit comprising at least two negative lenses and having anegative refracting power;

a second lens unit having a positive refracting power;

an aperture stop; and

a third lens unit having a positive refracting power.

In order to achieve the above-described second object, a projectionoptical system according to a third aspect of the embodiment is acatadioptric projection optical system for forming an image of a firstsurface on a second surface, the projection optical system comprising:

a first unit disposed in an optical path between the first surface andthe second surface and having a positive refracting power;

a second unit disposed in an optical path between the first unit and thesecond surface and comprising at least four mirrors;

a third unit disposed in an optical path between the second unit and thesecond surface, comprising at least two negative lenses, and having anegative refracting power; and

a fourth unit disposed in an optical path between the third unit and thesecond surface, comprising at least three positive lenses, and having apositive refracting power,

wherein an intermediate image is formed in the second unit and whereinan aperture stop is provided in the fourth unit.

In order to achieve the above-described second object, a projectionoptical system according to a fourth aspect of the embodiment is acatadioptric projection optical system for forming an image of a firstsurface on a second surface, the projection optical system comprising:

a first imaging optical system comprising at least six mirrors, forforming a first intermediate image and a second intermediate image ofthe first surface; and

a second imaging optical system for relaying the second intermediateimage onto the second surface.

In order to achieve the above-described third object, an exposureapparatus according to a fifth aspect of the embodiment is an exposureapparatus for effecting an exposure of a pattern formed on a mask, ontoa photosensitive substrate, the exposure apparatus comprising:

an illumination system for illuminating the mask set on the firstsurface; and

the projection optical system according to any one of theabove-described aspects, for forming an image of the pattern formed onthe mask, on the photosensitive substrate set on the second surface.

In order to achieve the above-described third object, an exposure methodaccording to a sixth aspect of the embodiment is an exposure method ofeffecting an exposure of a pattern formed on a mask, onto aphotosensitive substrate, the exposure method comprising:

an illumination step of illuminating the mask on which the predeterminedpattern is formed; and

an exposure step of performing an exposure of the pattern of the maskset on the first surface, onto the photosensitive substrate set on thesecond surface, using the projection optical system as set forth in theabove.

The present invention will be more fully understood from the detaileddescription given hereinbelow and the accompanying drawings, which aregiven by way of illustration only and are not to be considered aslimiting the embodiment.

Further scope of applicability of the embodiment will become apparentfrom the detailed description given hereinafter. However, it should beunderstood that the detailed description and specific examples, whileindicating preferred embodiments of the invention, are given by way ofillustration only, since various changes and modifications within thespirit and scope of the invention will be apparent to those skilled inthe art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration schematically showing a configuration of anexposure apparatus according to an embodiment of the embodiment.

FIG. 2 is an illustration showing a positional relation between theoptical axis and an effective exposure area of arcuate shape formed on awafer in the embodiment.

FIG. 3 is an illustration schematically showing a configuration betweena boundary lens and a wafer in the first example of the embodiment.

FIG. 4 is an illustration schematically showing a configuration betweena boundary lens and a wafer in the second example of the embodiment.

FIG. 5 is an illustration showing a lens configuration of a projectionoptical system according to the first example of the embodiment.

FIG. 6 is a diagram showing the transverse aberration in the firstexample.

FIG. 7 is an illustration showing a lens configuration of a projectionoptical system according to the second example of the embodiment.

FIG. 8 is a diagram showing the transverse aberration in the secondexample.

FIG. 9 is an illustration showing a lens configuration of a catadioptricprojection optical system according to the third example.

FIG. 10 is an illustration showing a lens configuration of acatadioptric projection optical system according to the fourth example.

FIG. 11 is an illustration showing an exposure area on a wafer in thethird and fourth examples.

FIG. 12 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system in the third example.

FIG. 13 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system in the fourth example.

FIG. 14 is an illustration showing a lens configuration of acatadioptric projection optical system according to the fifth example.

FIG. 15 is an illustration showing a lens configuration of acatadioptric projection optical system according to the sixth example.

FIG. 16 is an illustration showing a lens configuration of acatadioptric projection optical system according to the seventh example.

FIG. 17 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system in the fifth example.

FIG. 18 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system in the sixth example.

FIG. 19 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system in the seventh example.

FIG. 20 is a flowchart of a method of producing semiconductor devices asmicrodevices.

FIG. 21 is a flowchart of a method of producing a liquid crystal displaydevice as a microdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the projection optical system according to the first aspect of theembodiment, the medium having the refractive index larger than 1.1 isinterposed in the optical path between the boundary lens and the imageplane (second surface), thereby increasing the image-side numericalaperture NA. In passing, “Resolution Enhancement of 157-nm Lithographyby Liquid Immersion” reported in “Massachusetts Institute of Technology”in “SPIE2002 Microlithography” by Mr. M. Switkes and Mr. M. Rothschilddescribes Fluorinert (Perfluoropolyethers: trade name of 3M, USA) andDeionized Water as candidates for media having the requiredtransmittance for light of wavelength λ of not more than 200 nm.

In the projection optical system according to the first aspect of theembodiment, the optical surface on the object side (first surface side)of the boundary lens is provided with the positive refracting power,whereby the reflection loss is reduced on this optical surface and, inturn, the large effective image-side numerical aperture can be secured.In the optical system having the high-refractive-index material likeliquid as the medium on the image side, it is feasible to increase theeffective image-side numerical aperture to not less than 1.0 and, inturn, to enhance the resolution. However, where the projectionmagnification is constant, the object-side numerical aperture alsoincreases with increase in the image-side numerical aperture; therefore,if the projection optical system is constructed of only refractingmembers, it will be difficult to satisfy the Petzval's condition and itwill result in failing to avoid the increase in the scale of the opticalsystem.

Therefore, the projection optical system according to the first aspectof the embodiment adopts the catadioptric system of the type comprisingat least two reflecting mirrors, in which every transmitting member andevery reflecting member with a refracting power (power) are arrangedalong the single optical axis and which has the effective imaging areaof the predetermined shape not including the optical axis. In theprojection optical system of this type, for example, through action of aconcave reflecting mirror, it is feasible to well correct for thechromatic aberration and to readily satisfy the Petzval's condition towell correct for the curvature of field, and the scale of the opticalsystem can be reduced.

The projection optical system of this type has the configuration whereinevery transmitting member (lenses or the like) and every reflectingmember with a power (concave reflecting mirrors or the like) arearranged along the single optical axis, which is preferable because thedegree of difficulty in production is considerably lower than in amulti-axis configuration wherein the optical members are arranged alongmultiple optical axes. However, in the case of the single-axisconfiguration wherein the optical members are arranged along the singleoptical axis, the chromatic aberration tends to be difficult to wellcorrect for, but this problem of correction for chromatic aberration canbe overcome, for example, by use of laser light with a narrowed spectralwidth like ArF laser light.

In this manner, the first aspect of the embodiment can realize therelatively compact projection optical system having the excellentimaging performance as well corrected for the various aberrations suchas chromatic aberration and curvature of field and being capable ofsecuring the large effective image-side numerical aperture while wellsuppressing the reflection loss on the optical surfaces. Therefore, anexposure apparatus and exposure method using the projection opticalsystem according to the first aspect of the embodiment are able toperform an exposure of a fine pattern to transcribe the pattern throughthe projection optical system having the excellent imaging performanceand the large effective image-side numerical aperture and therefore thehigh resolution.

In the first aspect of the embodiment, the projection optical system ispreferably arranged to have an even number of reflecting mirrors, i.e.,to form the image of the first surface on the second surface through aneven number of reflections. When the projection optical system in thisconfiguration is applied, for example, to the exposure apparatus andexposure method, not a mirror image (a flipped image) but an unmirrored(unflipped) image (erect image or inverted image) of the mask pattern,is formed on the wafer, whereby the ordinary masks (reticles) can beused as in the case of the exposure apparatus equipped with the dioptricprojection optical system.

In the first aspect of the embodiment, the projection optical systempreferably comprises: a first imaging optical system comprising twomirrors, which forms an intermediate image of the first surface; and asecond imaging optical system, which forms the intermediate image on thesecond surface; the second imaging optical system preferably comprisesthe following components in order of passage of a ray from theintermediate image side: a first field mirror of a concave shape; asecond field mirror; a first lens unit comprising at least two negativelenses and having a negative refracting power; a second lens unit havinga positive refracting power; an aperture stop; and a third lens unithaving a positive refracting power.

In this configuration, the intermediate image of the first surface isformed in the first imaging optical system, and it is thus feasible toreadily and securely achieve the optical path separation between thebeam toward the first surface and the beam toward the second surface,even in the case where the numerical apertures are increased of thecatadioptric projection optical system. Since the second imaging opticalsystem comprises the first lens unit having the negative refractingpower, the total length of the catadioptric projection optical systemcan be reduced, and adjustment for satisfying the Petzval's conditioncan be readily performed. Furthermore, the first lens unit relievesvariation due to the difference of field angles of the beam expanded bythe first field mirror, so as to suppress occurrence of aberration.Therefore, the good imaging performance can be achieved throughout theentire region in the exposure area, even in the case where theobject-side and image-side numerical apertures of the catadioptricprojection optical system are increased in order to enhance theresolution.

In the above-described configuration, preferably, the first imagingoptical system comprises a fourth lens unit having a positive refractingpower, a negative lens, a concave mirror, and an optical path separatingmirror; and the first imaging optical system is arranged as follows:light traveling in the first imaging optical system passes through thefourth lens unit and the negative lens, is then reflected by the concavemirror, and passes again through the negative lens to be guided to theoptical path separating mirror; the light reflected by the optical pathseparating mirror is reflected by the first field mirror and the secondfield mirror and thereafter directly enters the first lens unit in thesecond imaging optical system.

In this configuration, the projection optical system can be telecentricon the first surface side because the first imaging optical systemcomprises the fourth lens unit having the positive refracting power.Since the first imaging optical system comprises the negative lens andthe concave mirror, adjustment for satisfying the Petzval's conditioncan be readily performed by adjusting the negative lens and the concavemirror.

In the first aspect of the embodiment, the projection optical systempreferably comprises a first imaging optical system comprising at leastsix mirrors for forming a first intermediate image and a secondintermediate image of the first surface; and a second imaging opticalsystem, which relays the second intermediate image onto the secondsurface.

Since this configuration comprises at least six mirrors, the firstintermediate image and the second intermediate image can be formedwithout increase in the total length of the catadioptric projectionoptical system, and the good imaging performance can be achievedthroughout the entire region in the exposure area, even in the casewhere the object-side and the image-side numerical apertures of thecatadioptric projection optical system are increased in order to enhancethe resolution.

In the aforementioned configuration, preferably, the first intermediateimage is formed between a mirror that light emerging from the firstsurface enters second and a mirror that the light emerging from thefirst surface enters fourth, out of the at least six mirrors in thefirst imaging optical system.

In this configuration, the first intermediate image is formed betweenthe mirror that the light emerging from the first surface enters secondand the mirror that the light emerging from the first surface entersfourth. Therefore, even in the case where the object-side and image-sidenumerical apertures of the catadioptric projection optical system areincreased in order to enhance the resolution, it is feasible to readilyand securely achieve the optical path separation between the beam towardthe first surface and the beam toward the second surface and to achievethe good imaging performance throughout the entire region in theexposure area.

Incidentally, since it is necessary to form the intermediate image nearthe pupil position in order to construct the catadioptric projectionoptical system of the single optical axis according to the first aspectof the embodiment, it is desirable to construct the projection opticalsystem as a reimaging optical system. In order to avoid mechanicalinterference between optical members while achieving the optical pathseparation with the intermediate image being formed near the pupilposition of the first imaging, the pupil diameter of the first imagingneeds to be set as small as possible even in the case where theobject-side numerical aperture is large; therefore, the first imagingoptical system with the small numerical aperture is desirably acatadioptric system.

In the first aspect of the embodiment, therefore, the projection opticalsystem preferably comprises: a first imaging optical system comprisingat least two reflecting mirrors, which forms an intermediate image ofthe first surface; and a second imaging optical system, which forms afinal image on the second surface on the basis of a beam from theintermediate image. In this case, specifically, the first imagingoptical system can be constructed using a first lens unit with apositive refracting power, a first reflecting mirror disposed in anoptical path between the first lens unit and the intermediate image, anda second reflecting mirror disposed in an optical path between the firstreflecting mirror and the intermediate image.

Preferably, the first reflecting mirror is a concave reflecting mirrordisposed near a pupil plane of the first imaging optical system, and atleast one negative lens is disposed in back-and-forth optical path (adouble optical path) formed by the concave reflecting mirror. By thisconfiguration wherein the negative lens is disposed in theback-and-forth optical path formed by the concave reflecting mirror inthe first imaging optical system, it becomes feasible to well correctfor the curvature of field while readily satisfying the Petzval'scondition, and to well correct for the chromatic aberration as well.

The negative lens in the back-and-forth optical path is desirablydisposed near the pupil position, but the clear aperture of the negativelens becomes smaller because the pupil diameter of the first imagingneeds to be kept as small as possible; therefore, the fluence (=energyamount per unit area and unit pulse) tends to become higher at thenegative lens. Therefore, if the negative lens is made of silica, alocal index change or compaction will become likely to occur due tovolumetric shrinkage under irradiation with laser light, and, in turn,the imaging performance of the projection optical system will degrade.

Likewise, the boundary lens located in the vicinity of the image planealso has a small clear aperture and the fluence is likely to become highthere. Therefore, if the boundary lens is made of silica, it will resultin likely causing the compaction and degrading the imaging performance.In the first aspect of the embodiment, the degradation of imagingperformance due to the compaction can be avoided by a configurationwherein the negative lens disposed in the back-and-forth optical pathformed by the concave reflecting mirror in the first imaging opticalsystem and the boundary lens disposed in the vicinity of the image planein the second imaging optical system are made of fluorite.

In the first aspect of the embodiment, the projection optical systemdesirably satisfies Condition (1) below. In Condition (1), F1 is thefocal length of the first lens unit, and Y₀ a maximum image height onthe second surface.

5<F1/Y ₀<15  (1)

The range above the upper limit of Condition (1) is undesirable becausethe pupil diameter of the first imaging is too large to avoid mechanicalinterference between optical members as described above. On the otherhand, the range below the lower limit of Condition (1) is undesirablebecause there occurs a large difference depending upon object heightsamong angles of incident light to the reflecting mirror (field angledifference) and it becomes difficult to achieve correction foraberrations such as coma and curvature of field. For betterdemonstrating the effect of the embodiment, the upper limit of Condition(1) is more preferably set to 13 and the lower limit thereof to 7.

In the first aspect of the embodiment, the first lens unit preferablycomprises at least two positive lenses. This configuration permits thepositive refracting power of the first lens unit to be set to a largevalue to readily satisfy Condition (1) and it is thus feasible to wellcorrect for coma, distortion, astigmatism, and so on.

It is difficult to produce a reflecting mirror with high reflectance andhigh endurance, and use of many reflecting surfaces will result in lossin optical quantity. In the first aspect of the embodiment, therefore,where the projection optical system is applied, for example, to theexposure apparatus and exposure method, the second imaging opticalsystem is preferably a dioptric system comprised of only a plurality oftransmitting members, in view of improvement in throughput.

Fluorite is a crystal material having intrinsic birefringence, and atransmitting member made of fluorite is considerably affected bybirefringence, particularly, for light of wavelength of not more than200 nm. For this reason, an optical system including such fluoritetransmitting members needs to suppress the degradation of the imagingperformance due to birefringence by combining the fluorite transmittingmembers of different orientations of crystal axes, but even suchcountermeasures cannot completely suppress the performance degradationdue to birefringence.

Furthermore, it is known that the refractive index distribution insidefluorite has high-frequency components, and the variation in refractiveindices including such high-frequency components causes flare to easilydegrade the imaging performance of the projection optical system;therefore, it is preferable to avoid use of fluorite as much aspossible. For decreasing use of fluorite as much as possible, therefore,the embodiment is preferably arranged so that 70% or more of thetransmitting members constituting the second imaging optical system ofthe dioptric system are made of silica.

In the first aspect of the embodiment, desirably, the effective imagingarea has an arcuate shape and the projection optical system satisfiesCondition (2) below. In Condition (2), R is a radius of curvature of anarc defining the effective imaging area, and Y₀ a maximum image heighton the second surface as described previously.

1.05<R/Y ₀<12  (2)

In the first aspect of the embodiment, the projection optical system hasthe effective imaging area of arcuate shape not including the opticalaxis, whereby the optical path separation can be readily achieved whileavoiding the increase in the scale of the optical system. However, forexample, where the projection optical system is applied to the exposureapparatus and exposure method, it is difficult to uniformly illuminatean illumination area of arcuate shape on the mask. Therefore, a methodto be adopted is one of limiting an illumination beam of rectangularshape corresponding to a rectangular region including the area of thearcuate shape, by a field stop having an aperture (light transmittingportion) of arcuate shape. In this case, in order to reduce loss inlight quantity due to the field stop, it is necessary to keep the radiusR of curvature of the arc defining the effective imaging area as largeas possible.

Namely, the range below the lower limit of Condition (2) is undesirablebecause the radius R of curvature is so small that the beam loss due tothe field stop becomes so large as to decrease the throughput due toreduction of illumination efficiency. On the other hand, the range abovethe upper limit of Condition (2) is undesirable because the radius R ofcurvature is so large that the required aberration-corrected areabecomes large in order to secure the effective imaging area in arequired width for reduction in overrun length during scan exposure, soas to result in increase in the scale of the optical system. For betterdemonstrating the effect of the embodiment, the upper limit of Condition(2) is more preferably set to 8 and the lower limit thereof to 1.07.

In the catadioptric projection optical system of the aforementionedtype, even in the case where the optical path to the image plane (secondsurface) is not filled with the medium like liquid, when the projectionoptical system satisfies Condition (2), it is feasible to avoid thereduction of throughput due to the decrease of illumination efficiencyand to avoid the increase in the scale of the optical system due to theincrease in the required aberration-corrected area. Where the projectionoptical system of the embodiment is applied to the exposure apparatusand exposure method, it is preferable to use, for example, ArF laserlight (wavelength 193.306 nm) as the exposure light, in view of thetransmittance of the medium (liquid or the like) filled between theboundary lens and the image plane, the degree of narrowing of the laserlight, and so on.

The projection optical system according to the second aspect of theembodiment is a catadioptric projection optical system for forming animage of a first surface on a second surface, comprising: a firstimaging optical system comprising two mirrors, which forms anintermediate image of the first surface; and a second imaging opticalsystem, which forms the intermediate image on the second surface,wherein the second imaging optical system comprises the followingcomponents in order of passage of a ray from the intermediate imageside: a first field mirror of a concave shape; a second field mirror; afirst lens unit comprising at least two negative lenses and having anegative refracting power; a second lens unit having a positiverefracting power; an aperture stop; and a third lens unit having apositive refracting power.

Since in this configuration the intermediate image of the first surfaceis formed in the first imaging optical system, it is feasible to readilyand securely achieve the optical path separation between the beam towardthe first surface and the beam toward the second surface, even in thecase where the numerical apertures of the catadioptric projectionoptical system are increased. Since the second imaging optical systemcomprises the first lens unit having the negative refracting power, thetotal length of the catadioptric projection optical system can bedecreased and the adjustment for satisfying the Petzval's condition canbe readily performed. Furthermore, the first lens unit relieves thevariation due to the difference of field angles of the beam expanded bythe first field mirror, so as to suppress occurrence of aberration.Therefore, even in the case where the object-side and image-sidenumerical apertures of the catadioptric projection optical system areincreased in order to enhance the resolution, good imaging performancecan be achieved throughout the entire region in the exposure area.

In the projection optical system according to the second aspect of theembodiment, preferably, the first imaging optical system comprises afourth lens unit having a positive refracting power, a negative lens, aconcave mirror, and an optical path separating mirror; and the firstimaging optical system is arranged as follows: light traveling in thefirst imaging optical system passes through the fourth lens unit and thenegative lens, is then reflected by the concave mirror, and passes againthrough the negative lens to be guided to the optical path separatingmirror; the light reflected by the optical path separating mirror isreflected by the first field mirror and the second field mirror andthereafter directly enters the first lens unit in the second imagingoptical system.

Since in this configuration the first imaging optical system comprisesthe fourth lens unit having the positive refracting power, theprojection optical system can be made telecentric on the first surfaceside. Since the first imaging optical system comprises the negative lensand the concave mirror, the adjustment for satisfying the Petzval'scondition can be readily performed by adjusting the negative lens andthe concave mirror.

In the projection optical system according to the second aspect of theembodiment, preferably, the first field mirror outputs light enteringthe first field mirror, so as to bend the light into a direction towardthe optical axis of the catadioptric projection optical system.

In the projection optical system according to the second aspect of theembodiment, preferably, the second field mirror has a convex shape.

According to these configurations, a ray incident to the first fieldmirror is outputted as bent into a direction toward the optical axis ofthe catadioptric system, whereby the second field mirror can beconstructed in a compact size even in the case where the numericalapertures of the catadioptric projection optical system are increased.Accordingly, the optical path separation between the beam toward thefirst surface and the beam toward the second surface can be readilyperformed even in the case where the object-side and image-sidenumerical apertures are increased in order to enhance the resolution.

In the projection optical system according to the second aspect of theembodiment, preferably, the two mirrors in the first imaging opticalsystem are a mirror of a concave shape and a mirror of a convex shapewhich are arranged in order of incidence of light from the firstsurface, and wherein the second field mirror in the second imagingoptical system is a mirror of a convex shape.

According to this configuration, the two mirrors in the first imagingoptical system are of the concave shape and the convex shape, and thesecond field mirror has the convex shape; therefore, it is feasible toreadily and securely guide the beam emerging from the first imagingoptical system, to the second imaging optical system.

In the projection optical system according to the second aspect of theembodiment, the aperture stop is disposed between the first field mirrorand the second surface, and the projection optical system satisfies thefollowing condition:

0.17<Ma/L<0.6,

where Ma is a distance on an optical axis between the first field mirrorand the second surface, and L a distance between the first surface andthe second surface.

According to this configuration, Ma/L is larger than 0.17, and it isthus feasible to avoid mechanical interference of the first field mirrorwith the first lens unit and with the second lens unit. Since Ma/L issmaller than 0.6, it is feasible to avoid an increase in the totallength and an increase in the size of the catadioptric projectionoptical system.

In the projection optical system according to the second aspect of theembodiment, preferably, the first lens unit in the second imagingoptical system has at least one aspherical lens.

According to this configuration, at least one of optical elementsconstituting the first lens unit is a lens of aspherical shape and thusgood imaging performance can be achieved throughout the entire region inthe exposure area, even in the case where the object-side and image-sidenumerical apertures are increased.

The projection optical system according to the third aspect of theembodiment is a catadioptric projection optical system, which forms animage of a first surface on a second surface, comprising: a first unitdisposed in an optical path between the first surface and the secondsurface and having a positive refracting power; a second unit disposedin an optical path between the first unit and the second surface andcomprising at least four mirrors; a third unit disposed in an opticalpath between the second unit and the second surface, comprising at leasttwo negative lenses, and having a negative refracting power; and afourth unit disposed in an optical path between the third unit and thesecond surface, comprising at least three positive lenses, and having apositive refracting power, wherein an intermediate image is formed inthe second unit and wherein an aperture stop is provided in the fourthunit.

In the projection optical system according to the third aspect of theembodiment, the intermediate image of the first surface is formed in thesecond unit and it is thus feasible to readily and securely achieve theoptical path separation between the beam toward the first surface andthe beam toward the second surface, even in the case where the numericalapertures of the catadioptric projection optical system are increased.Since the projection optical system comprises the third unit having thenegative refracting power, the total length of the catadioptricprojection optical system can be decreased and the adjustment forsatisfying the Petzval's condition can be readily performed. Therefore,the good imaging performance can be achieved throughout the entireregion in the exposure area, even in the case where the object-side andimage-side numerical apertures of the catadioptric projection opticalsystem are increased in order to enhance the resolution.

In the projection optical system according to the third aspect of theembodiment, preferably, the second unit comprises the followingcomponents in order of incidence of light from the first surface: afirst reflecting mirror of a concave shape; a second reflecting mirrorof a convex shape; a third reflecting mirror of a concave shape; and afourth reflecting mirror of a convex shape.

According to this configuration, the second unit comprises the concavemirror, the convex mirror, the concave mirror, and the convex mirror inorder of incidence of light from the first surface, and it is thusfeasible to readily and securely guide the beam emerging from the firstimaging optical system, to the second imaging optical system.

In the projection optical system according to the third aspect of theembodiment, preferably, the second unit comprises at least one negativelens, and an optical element located nearest to the third unit in theoptical path of the second unit is the fourth reflecting mirror or adouble pass lens through which light passes twice.

According to this configuration, since the optical element locatednearest to the third unit in the optical path of the second unit is thefourth reflecting mirror or the double pass lens through which the lightpasses twice, the adjustment for satisfying the Petzval's condition canbe readily performed by adjusting the lens in the third unit having thenegative refracting power, and the fourth reflecting mirror or thedouble pass lens.

In the projection optical system according to the third aspect of theembodiment, preferably, the third reflecting mirror outputs lightentering the third reflecting mirror, so as to bend the light into adirection toward the optical axis of the catadioptric projection opticalsystem.

This configuration enables miniaturization of the fourth reflectingmirror because a ray incident to the third reflecting mirror isoutputted as bent into a direction toward the optical axis of thecatadioptric projection optical system. Therefore, it is feasible toreadily and securely achieve the optical path separation between thebeam toward the first surface and the beam toward the second surface,even in the case where the object-side and image-side numericalapertures are increased in order to enhance the resolution.

In the projection optical system according to the third aspect of theembodiment, the aperture stop is disposed between the third reflectingmirror and the second surface, and the projection optical systemsatisfies the following condition:

0.17<Ma/L<0.6,

where Ma is a distance on an optical axis between the third reflectingmirror and the second surface, and L a distance between the firstsurface and the second surface.

In this configuration, Ma/L is larger than 0.17, and it is thus feasibleto avoid mechanical interference of the third reflecting mirror with thesecond unit and with the third unit. Since Ma/L is smaller than 0.6, itis feasible to avoid an increase in the total length and an increase inthe size of the catadioptric projection optical system.

In the projection optical system according to the third aspect of theembodiment, the third unit comprises at least one aspherical lens. Sincein this configuration at least one of optical elements constituting thethird unit is the aspherical lens, good imaging performance can beachieved throughout the entire region in the exposure area, even in thecase where the object-side and image-side numerical apertures areincreased.

The projection optical system according to the fourth aspect of theembodiment is a catadioptric projection optical system, which forms animage of a first surface on a second surface, the projection opticalsystem comprising: a first imaging optical system comprising at leastsix mirrors, which forms a first intermediate image and a secondintermediate image of the first surface; and a second imaging opticalsystem, which relays the second intermediate image onto the secondsurface.

Since the projection optical system according to the fourth aspect ofthe embodiment comprises at least six mirrors, the first intermediateimage and the second intermediate image can be formed, without increasein the total length of the catadioptric projection optical system, andgood imaging performance can be achieved throughout the entire region inthe exposure area, even in the case where the object-side and image-sidenumerical apertures of the catadioptric projection optical system areincreased in order to enhance the resolution.

In the projection optical system according to the fourth aspect of theembodiment, preferably, the first intermediate image is formed between amirror that light emerging from the first surface enters second and amirror that the light emerging from the first surface enters fourth, outof said at least six mirrors in the first imaging optical system.

In this configuration, the first intermediate image is formed betweenthe mirror that the light emerging from the first surface enters secondand the mirror that the light emerging from the first surface entersfourth. Therefore, it is feasible to readily and securely achieve theoptical path separation between the beam toward the first surface andthe beam toward the second surface and to obtain good imagingperformance throughout the entire region in the exposure area, even inthe case where the object-side and image-side numerical apertures of thecatadioptric projection optical system are increased in order to enhancethe resolution.

In the projection optical system according to the fourth aspect of theembodiment, preferably, the first imaging optical system comprises afield lens unit comprised of a transmitting optical element and having apositive refracting power, and the at least six mirrors are arranged soas to continuously reflect light transmitted by the field lens unit.

Since in this configuration the first imaging optical system comprisesthe field lens unit with the positive refracting power comprised of thetransmitting optical element, distortion or the like can be correctedfor by this field lens unit and the projection optical system can bemade telecentric on the first surface side. Since no lens is disposed inoptical paths between the at least six mirrors, it is feasible to securea region for holding each mirror and to readily hold each mirror. Sincethe light is continuously reflected by each mirror, the Petzval'scondition can be readily satisfied by adjusting each mirror.

In the projection optical system according to the fourth aspect of theembodiment, the first imaging optical system preferably comprises afield lens unit comprised of a transmitting optical element and having apositive refracting power, and the first imaging optical systempreferably comprises at least one negative lens between a mirror thatlight emerging from the first surface enters first and a mirror that thelight emerging from the first surface enters sixth, out of the at leastsix mirrors.

Since in this configuration the first imaging optical system comprisesthe field lens unit with the positive refracting power comprised of thetransmitting optical element, the projection optical system can be madetelecentric on the first surface side. Since the optical systemcomprises at least one negative lens between the mirror that the lightemerging from the first surface enters first and the mirror that thelight emerging from the first surface enters sixth, correction forchromatic aberration can be readily made by adjusting this negative lensand it is easy to make such adjustment as to satisfy the Petzval'scondition.

In the projection optical system according to the fourth aspect of theembodiment, preferably, every optical element constituting the secondimaging optical system is a transmitting optical element to form areduced image of the first surface on the second surface.

This configuration is free of the optical path separation load becauseevery optical element forming the second imaging optical system is atransmitting optical element. Therefore, the image-side numericalaperture of the catadioptric projection optical system can be increasedand the reduced image can be formed at a high reduction rate on thesecond surface. It is also feasible to readily correct for coma andspherical aberration.

In the projection optical system according to the fourth aspect of theembodiment, preferably, the second imaging optical system comprises thefollowing components in order of passage of light emerging from thefirst imaging optical system: a first lens unit having a positiverefracting power; a second lens unit having a negative refracting power;a third lens unit having a positive refracting power; an aperture stop;and a fourth lens unit having a positive refracting power.

According to this configuration, the first lens unit with the positiverefracting power, the second lens unit with the negative refractingpower, the third lens unit with the positive refracting power, theaperture stop, and the fourth lens unit with the positive refractingpower constituting the second imaging optical system advantageouslyfunction to satisfy the Petzval's condition. It is also feasible toavoid an increase in the total length of the catadioptric projectionoptical system.

In the projection optical system according to the fourth aspect of theembodiment, a mirror disposed at a position where light emerging fromthe first surface is most distant from the optical axis of thecatadioptric projection optical system, out of the at least six mirrorsis preferably a mirror of a concave shape, and the aperture stop ispreferably disposed between the mirror of the concave shape and thesecond surface. Preferably, the projection optical system satisfies thefollowing condition:

0.2<Mb/L<0.7,

where Mb is a distance on an optical axis between the mirror of theconcave shape and the second surface and L a distance between the firstsurface and the second surface.

In this configuration, since Mb/L is larger than 0.2, it is feasible toavoid mechanical interference of the mirror of the concave shape locatedat the position most distant from the optical axis of the catadioptricprojection optical system, with the first lens unit, the second lensunit, and the third lens unit. Since Mb/L is smaller than 0.7, it isfeasible to avoid an increase in the total length and an increase in thesize of the catadioptric projection optical system.

In the projection optical system according to the fourth aspect of theembodiment, preferably, the second lens unit and the fourth lens unithave at least one aspherical lens.

Since in this configuration at least one of optical elementsconstituting the second lens unit and the fourth lens unit is a lens ofaspherical shape, it is feasible to readily make the aberrationcorrection and to avoid an increase in the total length of thecatadioptric projection optical system. Therefore, good imagingperformance can be achieved throughout the entire region in the exposurearea, even in the case where the object-side and image-side numericalapertures are increased.

The projection optical system according to the fourth aspect of theembodiment is preferably as follows: the catadioptric projection opticalsystem is a thrice-imaging (three time) optical system, which forms thefirst intermediate image being an intermediate image of the firstsurface, and the second intermediate image being an image of the firstintermediate image, in an optical path between the first surface and thesecond surface.

In this configuration, the projection optical system is thethrice-imaging optical system, whereby the first intermediate image isan inverted image of the first surface, the second intermediate image isan erect image of the first surface, and the image formed on the secondsurface is an inverted image. Therefore, in the case where thecatadioptric projection optical system is mounted on the exposureapparatus and where an exposure is carried out with scanning of thefirst surface and the second surface, the scanning direction of thefirst surface can be made opposite to the scanning direction of thesecond surface, and it is easy to perform such adjustment as to decreasea change in the center of gravity of the entire exposure apparatus. Itis also feasible to reduce vibration of the catadioptric projectionoptical system caused by the change in the center of gravity of theentire exposure apparatus, and good imaging performance can be achievedthroughout the entire region in the exposure area.

The projection optical systems according to the second aspect to thefourth aspect of the embodiment are characterized in that a lens surfaceon the first surface side of a lens located nearest to the secondsurface out of lenses in the catadioptric projection optical system hasa positive refracting power, and in that, where a refractive index of anatmosphere in the catadioptric projection optical system is 1, a mediumhaving a refractive index larger than 1.1 is interposed in an opticalpath between the lens nearest to the second surface, and the secondsurface.

In this configuration, the medium having the refractive index largerthan 1.1 is interposed in the optical path between the lens locatednearest to the second surface in the catadioptric projection opticalsystem and the second surface, the wavelength of exposure light in themedium is 1/n times that in air where the refractive index of the mediumis n, and thus the resolution can be enhanced.

The projection optical systems according to the second aspect to thefourth aspect of the embodiment are preferably configured so that anoptical axis of every optical element with a predetermined refractingpower in the catadioptric projection optical system is arrangedsubstantially on a single straight line, and so that a region of animage formed on the second surface by the catadioptric projectionoptical system is an off-axis region not including the optical axis.

According to this configuration, the optical axis of every opticalelement in the catadioptric projection optical system is arrangedsubstantially on the single straight line, and it is thus feasible toreduce the degree of difficulty of production in production of thecatadioptric projection optical system and to readily perform relativeadjustment of each optical member.

The exposure apparatus according to the fifth aspect of the embodimentis an exposure apparatus for effecting an exposure of a pattern formedon a mask, onto a photosensitive substrate, comprising: an illuminationsystem, which illuminates the mask set on the first surface; and theprojection optical system according to any one of the first aspect tothe fourth aspect of the embodiment, which forms an image of the patternformed on the mask, on the photosensitive substrate set on the secondsurface.

According to this configuration, the exposure apparatus comprises thecompact catadioptric projection optical system with the large numericalaperture, and thus the exposure apparatus is able to suitably perform anexposure of a fine pattern on the photosensitive substrate.

In the exposure apparatus according to the fifth aspect of theembodiment, preferably, the illumination system supplies illuminationlight which is s-polarized light with respect to the second surface.This configuration enhances the contrast of the image formed on thephotosensitive substrate and secures a large depth of focus (DOF).Particularly, the projection optical systems according to the firstaspect to the fourth aspect of the embodiment permit the optical pathseparation to be achieved without use of an optical path deflectingmirror (bending mirror) having a function of deflecting the opticalaxis. There is a high risk of causing a large phase difference betweenp-polarized light and s-polarized light reflected by the optical pathdeflecting mirror, and in use of the optical path deflecting mirror, itbecomes difficult to supply illumination light of s-polarized light withrespect to the second surface, because of this reflection phasedifference; namely, there arises a problem that the illumination lightis not s-polarized light on the second surface even through generationof polarization in the circumferential direction with respect to theoptical axis of the illumination optical device. In contrast to it, thisproblem hardly occurs in the projection optical systems according to thefirst aspect to the fourth aspect of the embodiment.

In the exposure apparatus according to the fifth aspect of theembodiment, preferably, the projection exposure of the pattern of themask onto the photosensitive substrate is performed while moving themask and the photosensitive substrate along a predetermined directionrelative to the projection optical system.

The exposure method according to the sixth aspect of the embodiment isan exposure method of effecting an exposure of a pattern formed on amask, onto a photosensitive substrate, comprising: an illumination stepof illuminating the mask on which the predetermined pattern is formed;and an exposure step of performing an exposure of the pattern of themask set on the first surface, onto the photosensitive substrate set onthe second surface, using the projection optical system according to anyone of the first aspect to the fourth aspect of the embodiment.

In this configuration, the exposure is performed by the exposureapparatus including the compact catadioptric projection optical systemwith the large numerical aperture, whereby a fine pattern can besuitably exposed.

Embodiments of the embodiment will be described below with reference tothe drawings.

FIG. 1 is a schematic configuration diagram showing an embodiment of theexposure apparatus of the embodiment.

In FIG. 1, the exposure apparatus EX has a reticle stage RST supportinga reticle R (mask), a wafer stage WST supporting a wafer W as asubstrate, an illumination optical system IL for illuminating thereticle R supported by the reticle stage RST, with exposure light EL, aprojection optical system PL for performing a projection exposure of animage of a pattern on the reticle R illuminated with the exposure lightEL, onto the wafer W supported by the wafer stage WST, a liquid supplydevice 1 for supplying a liquid 50 onto the wafer W, a recovery device20 for collecting the liquid 50 flowing out of the wafer W, and acontroller CONT for totally controlling the overall operation of theexposure apparatus EX.

The present embodiment will be described using as an example a casewhere the exposure apparatus EX is a scanning exposure apparatus forperforming an exposure of a pattern formed on the reticle R, onto thewafer W while synchronously moving the reticle R and wafer W along ascanning direction (so called a scanning stepper). In the descriptionbelow, a direction coinciding with the optical axis AX of the projectionoptical system PL is defined as a Z-axis direction, the synchronousmovement direction (scanning direction) of the reticle R and wafer W inthe plane normal to the Z-axis direction, as an X-axis direction, and adirection (non-scanning direction) normal to the Z-axis direction andthe Y-axis direction as a Y-axis direction. Directions around theX-axis, around the Y-axis, and around the Z-axis are defined as θX, θY,and θZ directions, respectively. The “wafer” encompasses a semiconductorwafer coated with a resist, and the “reticle” encompasses a mask with adevice pattern to be projected at an enlargement, reduction, or unitmagnification onto the wafer.

The illumination optical system IL is a system for illuminating thereticle R supported by the reticle stage RST, with the exposure lightEL, based on the exposure light from a light source 100 for supplyingthe illumination light in the ultraviolet region. The illuminationoptical system IL has an optical integrator for uniformizing theilluminance of a beam emitted from the light source 100, a condenserlens for condensing the exposure light EL from the optical integrator, arelay lens system, a variable field stop for defining an illuminationarea in a slit shape on the reticle R with the exposure light EL, and soon. Here the illumination optical system IL is provided with ans-polarized light converter 110 for converting linearly polarized lightfrom the light source 100, into polarized light as s-polarized lightwith respect to the reticle R (wafer W), without substantial loss oflight quantity. The s-polarized light converter of this type isdisclosed, for example, in Japanese Patent No. 3246615.

A predetermined illumination area on the reticle R is illuminated withthe exposure light EL of a uniform illuminance distribution by theillumination optical system IL. The exposure light EL emitted from theillumination optical system IL is, for example, deep ultraviolet light(DUV light) such as the emission lines (g-line, h-line, and i-line) inthe ultraviolet region from a mercury lamp and KrF excimer laser light(wavelength 248 nm), or vacuum ultraviolet light (VUV light) such as ArFexcimer laser light (wavelength 193 nm) and F2 laser light (wavelength157 nm). The present embodiment is assumed to use the ArF excimer laserlight.

The reticle stage RST is a stage supporting the reticle R and istwo-dimensionally movable in the plane normal to the optical axis AX ofthe projection optical system PL, i.e., within the XY plane and finelyrotatable in the OZ direction. The reticle stage RST is driven by areticle stage driving device RSTD such as a linear motor. The reticlestage driving device RSTD is controlled by the controller CONT. Thetwo-dimensional position and an angle of rotation of the reticle Ron thereticle stage RST are measured in real time by a laser interferometer,and the result of the measurement is fed to the controller CONT. Thecontroller CONT drives the reticle stage driving device RSTD on thebasis of the measurement result of the laser interferometer to positionthe reticle R supported by the reticle stage RST.

The projection optical system PL is one for performing a projectionexposure of a pattern on the reticle R at a predetermined projectionmagnification β onto the wafer W, and is composed of a plurality ofoptical elements (lenses), which are supported by a lens barrel PK as ametal member. In the present embodiment, the projection optical systemPL is a reduction system with the projection magnification β of ¼ or ⅕,for example. The projection optical system PL may be either of a 1:1system and an enlarging system. An optical element (lens) 60 is exposedfrom the lens barrel PK on the distal end side (wafer W side) of theprojection optical system PL of the present embodiment. This opticalelement 60 is detachably (replaceably) attached to the lens barrel PK.

The wafer stage WST is a stage supporting the wafer W, and is providedwith a Z-stage 51 holding the wafer W through the wafer holder, an XYstage 52 supporting the Z-stage 51, and a base 53 supporting the XYstage 52. The wafer stage WST is driven by a wafer stage driving deviceWSTD such as a linear motor. The wafer stage driving device WSTD iscontrolled by the controller CONT. As the Z-stage 51 is driven, thewafer W held by the Z-stage 51 is controlled as to the position in theZ-axis direction (focus position) and as to the position in the θX andθY directions. As the XY stage 52 is driven, the wafer W is controlledas to the position in the XY directions (the position in the directionssubstantially parallel to the image plane of the projection opticalsystem PL). Namely, the Z-stage 51 controls the focus position and angleof inclination of the wafer W to match the surface of the wafer W withthe image plane of the projection optical system PL by the autofocusmethod and autoleveling method, and the XY stage 52 positions the waferW in the X-axis direction and in the Y-axis direction. It is needless tomention that the Z-stage and XY stage may be integrally arranged.

A moving mirror 54 is provided on the wafer stage WST (Z-stage 51). Aninterferometer 55 is disposed at the position opposite to the movingmirror 54. The two-dimensional position and the angle of rotation of thewafer W on the wafer stage WST are measured in real time by the laserinterferometer 55, and the result of the measurement is fed to thecontroller CONT. The controller CONT drives the wafer stage drivingdevice WSTD on the basis of the measurement result of the laserinterferometer 55 to position the wafer W supported by the wafer stageWST.

The present embodiment adopts the liquid immersion method, in order tosubstantially shorten the exposure wavelength so as to improve theresolution and substantially widen the depth of focus. For this reason,the space between the surface of the wafer W and the end surface (lowerface) 7 of the optical element (lens) 60 on the wafer W side of theprojection optical system PL is filled with a predetermined liquid 50 atleast during the period of transcribing the image of the pattern of thereticle R onto the wafer W. As described above, the lens 60 is exposedon the end surface side of the projection optical system PL and theliquid 50 is arranged in contact with only the lens 60. This preventscorrosion or the like of the lens barrel PK made of metal. Since the endsurface 7 of the lens 60 is sufficiently smaller than the lens barrel PKof the projection optical system PL and the wafer W and since the liquid50 is kept in contact with only the lens 60 as described above, theliquid 50 is arranged to be locally filled on the image plane side ofthe projection optical system PL. Namely, the liquid-immersed portionbetween the projection optical system PL and the wafer W is sufficientlysmaller than the wafer W. The present embodiment uses pure water as theliquid 50. Pure water can transmit not only the ArF excimer laser light,but also the exposure light EL if the exposure light EL is the deepultraviolet light (DUV light) such as the emission lines (g-line,h-line, and i-line) in the ultraviolet region emitted from a mercurylamp and the KrF excimer laser light (wavelength 248 nm), for example.

The exposure apparatus EX is provided with the liquid supplying device 1for supplying the predetermined liquid 50 to the space 56 between theend surface (distal end face of lens 60) 7 of the projection opticalsystem PL and the wafer W, and a liquid recovery device 2 as a secondrecovery device for collecting the liquid 50 in the space 56, i.e., theliquid 50 on the wafer W. The liquid supplying device 1 is a device forlocally filling the space on the image plane side of the projectionoptical system PL with the liquid 50, and is provided with a tank forstoring the liquid 50, a compression pump, and a temperature regulatorfor regulating the temperature of the liquid 50 to be supplied to thespace 56. One end of supply tube 3 is connected to the liquid supplyingdevice 1 and the other end of the supply tube 3 is connected to a supplynozzle 4. The liquid supplying device 1 supplies the liquid 50 to thespace 56 through the supply tube 3 and supply nozzle 4.

The liquid recovery device 2 is provided with a suction pump, a tank forstoring the collected liquid 50, and so on. One end of recovery tube 6is connected to the liquid recovery device 2 and the other end of therecovery tube 6 is connected to a collection nozzle 5. The liquidrecovery device 2 collects the liquid 50 in the space 56 through thecollection nozzle 5 and recovery tube 6. For filling the space 56 withthe liquid 50, the controller CONT drives the liquid supplying device 1to supply the liquid 50 in a predetermined amount per unit time throughthe supply tube 3 and supply nozzle 4 to the space 56, and drives theliquid recovery device 2 to collect the liquid 50 in a predeterminedamount per unit time through the collection nozzle 5 and recovery tube 6from the space 56. This results in placing the liquid 50 in the space 56between the end surface 7 of the projection optical system PL and thewafer W to form a liquid-immersed portion. Here the controller CONT canarbitrarily set the liquid supply amount per unit time to the space 56by controlling the liquid supplying device 1, and can also arbitrarilyset the liquid collection amount per unit time from on the wafer W bycontrolling the liquid recovery device 2.

FIG. 2 is an illustration showing a positional relation between theoptical axis and an effective exposure area of arcuate shape formed on awafer in the present embodiment. In the present embodiment, as shown inFIG. 2, a region well corrected for aberration, i.e.,aberration-corrected region AR is defined in an arcuate shape by acircle with an outside radius (radius) Ro centered around the opticalaxis AX, a circle with an inside radius (radius) Ri centered around theoptical axis AX, and two line segments parallel to the X-direction,spaced by a distance H. Then an effective exposure region (effectiveimaging area) ER is set in an arcuate shape by two arcs with a radius Rof curvature spaced in the X-direction, and two line segments of thelength D parallel with the X-direction as spaced by the distance H, soas to be substantially inscribed in the aberration-corrected region ARof arcuate shape.

In this manner, the entire effective imaging area ER of the projectionoptical system PL exists in the region off the optical axis AX. The sizealong the Y-direction of the effective imaging area ER of arcuate shapeis H, and the size along the X-direction is D. Although not shown, theillumination area of arcuate shape (i.e., the effective illuminationarea) having the size and shape optically corresponding to the effectiveexposure region ER of arcuate shape is thus formed not including theoptical axis AX, on the reticle R.

The exposure apparatus of the present embodiment is arranged so that theinterior of the projection optical system PL is kept in an airtightstate between an optical member located nearest to the reticle among theoptical members forming the projection optical system PL (which is lensL11 in the first and second examples, lens L1 in the third and fifthexamples, lens L21 in the fourth and sixth examples, or lens L51 in theseventh example) and a boundary lens Lb (lens L217 in the first andsecond examples, lens L18 in the third example, lens L36 in the fourthexample, lens L20 in the fifth example, lens L41 in the sixth example,or lens L70 in the seventh example) and so that the gas inside theprojection optical system PL is replaced with an inert gas such ashelium gas or nitrogen, or the inside is kept in a substantially vacuumstate. Furthermore, the members such as the reticle R and reticle stageRS are disposed in the narrow optical path between the illuminationoptical system IL and the projection optical system PL, and an interiorof a casing (not shown) for hermetically enclosing the reticle R, thereticle stage RS, etc. is filled with an inert gas such as nitrogen orhelium gas, or kept in a substantially vacuum state.

FIG. 3 is an illustration schematically showing a configuration betweenthe boundary lens and the wafer in the first example of the presentembodiment. With reference to FIG. 3, the boundary lens Lb in the firstexample has a convex surface kept toward the reticle (first surface). Inother words, the reticle-side surface Sb of the boundary lens Lb has apositive refracting power. The optical path between the boundary lens Lband the wafer W is filled with a medium Lm having the refractive indexlarger than 1.1. In the first example, deionized water is used as themedium Lm.

FIG. 4 is an illustration schematically showing a configuration betweenthe boundary lens and the wafer in the second example of the presentembodiment. With reference to FIG. 4, the boundary lens Lb in the secondexample also has a convex surface kept toward the reticle and thereticle-side surface Sb thereof has a positive refracting power as inthe first example. However, the second example is different from thefirst example in that a plane-parallel plate Lp is detachably arrangedin the optical path between the boundary lens Lb and the wafer W and inthat the optical path between the boundary lens Lb and theplane-parallel plate Lp and the optical path between the plane-parallelplate Lp and the wafer W are filled with the medium Lm having therefractive index larger than 1.1. In the second example deionized wateris also used as the medium Lm as in the first example.

The present embodiment is arranged so that during an exposure by thestep-and-scan method of performing a scanning exposure while moving thewafer W relative to the projection optical system PL, the liquid mediumLm is continuously filled in the optical path between the boundary lensLb of the projection optical system PL and the wafer W from start to endof the scanning exposure. Another potential configuration is such thatthe wafer holder table WT is constructed in a chamber shape so as toaccommodate the liquid (medium Lm) and that the wafer W is positionedand held by vacuum suction in the center of the inner bottom partthereof (in the liquid), as in the technology disclosed in JapanesePatent Application Laid-Open No. 10-303114, for example. In thisconfiguration, the distal end of the lens barrel of the projectionoptical system PL is arranged to reach the inside of the liquid and,consequently, the wafer-side optical surface of the boundary lens Lbreaches the inside of the liquid.

In this manner, an atmosphere with little absorption of the exposurelight is formed throughout the entire optical path from the light source100 to the substrate P. As described above, the illumination area on thereticle R and the exposure region (i.e., the effective exposure regionER) on the wafer W are of the arcuate shape extending in theX-direction. Therefore, the positions of the reticle R and substrate Ware controlled using the reticle stage controller RSTD, the substratestage driving device, the laser interferometers, etc. to synchronouslymove (scan) the reticle stage RST and the substrate stage WS, in turn,the reticle R and substrate (wafer) W along the X-direction, whereby thescanning exposure of the reticle pattern is performed in the exposureregion having a width equal to the Y-directional size H of the effectiveexposure region ER and a length according to a scan amount (movementamount) of the substrate W, on the substrate W.

In each example, an aspherical surface is expressed by mathematicalexpression (a) below, where y represents a height in a direction normalto the optical axis, z a distance (sag) along the optical axis from atangent plane at an apex of the aspherical surface to a position on theaspherical surface at the height y, r a radius of curvature at the apex,κ a conical coefficient, and C_(n) aspherical coefficients of order n.In each example, a lens surface formed in aspherical shape is providedwith mark * on the right side to a surface number.

z=(y ² /r)/[1+{1−(1+κ)·y ² /r ²}^(1/2) ]+c ₄ ·y ⁴ +c ₆ ·y ⁶ +c ₈ ·y ⁸ +c₁₀ ·y ¹⁰ +c ₁₂ ·y ¹² +c ₁₄ ·y ¹⁴ +c ₁₆ ·y ¹⁶ +c ₁₈ ·y ¹⁸ +c ₂₀ ·y²⁰  (a)

In the first and second examples, the values of the asphericalcoefficients C₁₆ to C₂₀ are 0, and thus the description thereof isomitted.

In each example, the projection optical system PL is composed of a firstimaging optical system G1 for forming an intermediate image (or anoptically conjugate point) of the pattern of the reticle R disposed onthe object plane (first surface), and a second imaging optical system G2for forming a reduced image (or an optically conjugate point) of thereticle pattern on the wafer W disposed on the image plane (secondsurface) on the basis of light from the intermediate image. Here thefirst imaging optical system G1 is a catadioptric system including afirst concave reflecting mirror CM1 and a second concave reflectingmirror CM2, and the second imaging optical system G2 a dioptric system.

First Example

FIG. 5 is an illustration showing a lens configuration of the projectionoptical system according to the first example of the present embodiment.With reference to FIG. 5, in the projection optical system PL accordingto the first example, the first imaging optical system G1 is composed ofthe following components arranged in order from the reticle side alongthe traveling direction of light: a biconvex lens L11 whose convexsurface of aspherical shape is kept toward the wafer; a biconvex lensL12; a negative meniscus lens L13 whose concave surface of asphericalshape is kept toward the reticle; and a first concave reflecting mirrorCM1. In the first imaging optical system G1, a reflecting surface ofsecond concave reflecting mirror CM2 for reflecting the light reflectedby the first concave reflecting mirror CM1 and transmitted by thenegative meniscus lens L13, toward the second imaging optical system G2is placed in a region not including the optical axis AX between thebiconvex lens L12 and the negative meniscus lens L13, Therefore, thebiconvex lens L11 and the biconvex lens L12 constitute a first lens unithaving a positive refracting power. The first concave reflecting mirrorCM1 constitutes a concave reflecting mirror disposed near the pupilplane of the first imaging optical system G1.

On the other hand, the second imaging optical system G2 is composed ofthe following components in order from the reticle side along thetraveling direction of light: a positive meniscus lens L21 whose concavesurface is kept toward the reticle; a biconvex lens L22; a positivemeniscus lens L23 whose concave surface of aspherical shape is kepttoward the wafer; a negative meniscus lens L24 whose convex surface ofaspherical shape is kept toward the reticle; a negative meniscus lensL25 whose convex surface is kept toward the reticle; a biconcave lensL26 whose concave surface of aspherical shape is kept toward thereticle; a positive meniscus lens L27 whose concave surface is kepttoward the reticle; a negative meniscus lens L28 whose convex surface ofaspherical shape is kept toward the reticle; a biconvex lens L29; abiconvex lens L210; a positive meniscus lens L211 whose convex surfaceis kept toward the reticle; an aperture stop AS; a positive meniscuslens L212 whose concave surface is kept toward the reticle; a biconvexlens L213; a positive meniscus lens L214 whose concave surface ofaspherical shape is kept toward the wafer; a positive meniscus lens L215whose convex surface is kept toward the reticle; a positive meniscuslens L216 whose concave surface of aspherical shape is kept toward thewafer; and a planoconvex lens L217 (boundary lens Lb) whose plane iskept toward the wafer.

In the first example, all the transmitting members (lenses) and all thereflecting members with a power (the first concave reflecting mirror CM1and the second concave reflecting mirror CM2) constituting theprojection optical system PL are arranged along the single optical axisAX. Specifically, 100% of the transmitting members forming the secondimaging optical system G2 are made of silica. The optical path betweenthe planoconvex lens L217 as the boundary lens Lb and the wafer W isfilled with the medium Lm consisting of deionized water. In the firstexample, the light from the reticle R passes through the lenses L11 toL13 to enter the first concave reflecting mirror CM1. The lightreflected by the first concave reflecting mirror CM1 travels via thelens L13 and the second concave reflecting mirror CM2 to form anintermediate image of the reticle R near the first concave reflectingmirror CM1. The light reflected by the second concave reflecting mirrorCM2 travels through the lenses L21 to L217 (Lb) to form a reduced imageof the reticle R on the wafer W.

In the first example, all the transmitting members (lenses) forming theprojection optical system PL are made of silica (SiO₂). The lasingcenter wavelength of the ArF excimer laser light being the exposurelight is 193.306 nm, and the refractive index of silica near 193.306 nmvaries at a rate of −1.591×10⁻⁶ per wavelength change of +1 pm, andvaries at a rate of +1.591×10⁻⁶ per wavelength change of −1 pm. In otherwords, the dispersion (dn/dλ) of the refractive index of silica is−1.591×10⁻⁶/pm near 193.306 nm. The refractive index of deionized waternear 193.306 nm varies at a rate of −2.6×10⁻⁶ per wavelength change of+1 pm and varies at a rate of +2.6×10⁻⁶ per wavelength change of −1 pm.In other words, the dispersion (dn/dλ) of the refractive index ofdeionized water is −2.6×10⁻⁶/pm near 193.306 nm.

In the first example, the refractive index of silica for the centerwavelength of 193.306 nm is 1.5603261, the refractive index of silicafor 193.306 nm+0.1 pm=193.3061 nm is 1.560325941, and the refractiveindex of silica for 193.306 nm−0.1 pm=193.3059 nm is 1.560326259. Therefractive index of deionized water for the center wavelength of 193.306nm is 1.47, the refractive index of deionized water for 193.306 nm+0.1pm=193.3061 nm is 1.46999974, and the refractive index of deionizedwater for 193.306 nm−0.1 pm=193.3059 nm is 1.47000026.

Table (1) below presents values of specifications of the projectionoptical system PL according to the first example. In Table (1), λrepresents the center wavelength of the exposure light, β a projectionmagnification (imaging magnification of the entire system), NA theimage-side (wafer-side) numerical aperture, Ro and Ri the outside radiusand inside radius of the aberration-corrected region AR, H and D theY-directional size and X-directional size of the effective exposureregion ER, R the radius of curvature of the arc defining the effectiveexposure region ER (effective imaging area) of arcuate shape, and Y₀ themaximum image height. Each surface, number represents an order of asurface from the reticle side along the traveling direction of rays fromthe reticle surface being the object plane (first surface) to the wafersurface being the image plane (second surface), r a radius of curvatureof each surface (radius of curvature at an apex: mm in the case of anaspherical surface), d an on-axis spacing or surface separation (mm) ofeach surface, and n the refractive index for the center wavelength.

The surface separation d changes its sign every reflection. Therefore,the sign of the surface separation d is negative in the optical pathfrom the first concave reflecting mirror CM1 to the second concavereflecting mirror CM2, and positive in the other optical paths. Theradius of curvature of each convex surface kept toward the reticle ispositive, and the radius of curvature of each concave surface kepttoward the reticle is negative, regardless of the direction of incidenceof light. The notations in Table (1) also apply to Table (2)hereinafter.

TABLE 1 Principal Specification λ = 193.306 nm β = +¼ NA = 1.04 Ro =17.0 mm Ri = 11.5 mm H = 26.0 mm D = 4.0 mm R = 20.86 mm Y₀ = 17.0 mmSpecification of Optical Members Surface number r d n Optical Member(reticle surface) 70.25543  1 444.28100 45.45677 1.5603261 (L11)  2*−192.24078 1.00000  3 471.20391 35.53423 1.5603261 (L12)  4 −254.24538122.19951  5* −159.65514 13.00000 1.5603261 (L13)  6 −562.86259 9.00564 7 −206.23868 −9.00564 (CM1)  8 −562.86259 −13.00000 1.5603261 (L13)  9*−159.65514 −107.19951 10 3162.83419 144.20515 (CM2) 11 −389.0121543.15699 1.5603261 (L21) 12 −198.92113 1.00000 13 3915.27567 42.010891.5603261 (L22) 14 −432.52137 1.00000 15 203.16777 62.58039 1.5603261(L23) 16* 515.92133 18.52516 17* 356.67027 20.00000 1.5603261 (L24) 18269.51733 285.26014 19 665.61079 35.16606 1.5603261 (L25) 20 240.5593832.43496 21* −307.83344 15.00000 1.5603261 (L26) 22 258.17867 58.2428423 −1143.34122 51.43638 1.5603261 (L27) 24 −236.25969 6.67292 25*1067.55487 15.00000 1.5603261 (L28) 26 504.02619 18.88857 27 4056.9765554.00381 1.5603261 (L29) 28 −283.04360 1.00000 29 772.31002 28.963071.5603261 (L210) 30 −8599.87899 1.00000 31 667.92225 52.94747 1.5603261(L211) 32 36408.68946 2.30202 33 ∞ 42.27703 (AS) 34 −2053.34123 30.000001.5603261 (L212) 35 −514.67146 1.00000 36 1530.45141 39.99974 1.5603261(L213) 37 −540.23726 1.00000 38 370.56341 36.15464 1.5603261 (L214) 39*12719.40982 1.00000 40 118.92655 41.83608 1.5603261 (L215) 41 190.401941.00000 42 151.52892 52.42553 1.5603261 (L216) 43* 108.67474 1.12668 4491.54078 35.50067 1.5603261 (L217:Lb) 45 ∞ 6.00000 1.47 (Lm) (Wafersurface) (Aspherical data) 2^(nd) surface κ = 0 C₄ = −8.63025 × 10⁻⁹ C₆= 2.90424 × 10⁻¹³ C₈ = 5.43348 × 10⁻¹⁷ C₁₀ = 1.65523 × 10⁻²¹ C₁₂ =8.78237 × 10⁻²⁶ C₁₄ = 6.53360 × 10⁻³⁰ 5th surface and 9^(th) surface(same surface) κ = 0 C₄ = 7.66590 × 10⁻⁹ C₆ = 6.09920 × 10⁻¹³ C₈ =−6.53660 × 10⁻¹⁷ C₁₀ = 2.44925 × 10⁻²⁰ C₁₂ = −3.14967 × 10⁻²⁴ C₁₄ =2.21672 × 10⁻²⁸ 16 th surface κ = 0 C₄ = −3.79715 × 10⁻⁸ C₆ = 2.19518 ×10⁻¹² C₈ = −9.40364 × 10⁻¹⁷ C₁₀ = 3.33573 × 10⁻²¹ C₁₂ = −7.42012 × 10⁻²⁶C₁₄ = 1.05652 × 10⁻³⁰ 17th surface κ = 0 C₄ = −6.69596 × 10⁻⁸ C₆ =1.67561 × 10⁻¹² C₈ = −6.18763 × 10⁻¹⁷ C₁₀ = 2.65428 × 10⁻²¹ C₁₂ =−4.09555 × 10⁻²⁶ C₁₄ = 3.25841 × 10⁻³¹ 21st surface κ = 0 C₄ = −8.68772× 10⁻⁸ C₆ = −1.30306 × 10⁻¹² C₈ = −2.65902 × 10⁻¹⁷ C₁₀ = −6.56830 ×10⁻²¹ C₁₂ = 3.66980 × 10⁻²⁵ C₁₄ = −5.05595 × 10⁻²⁹ 25th surface κ = 0 C₄= −1.54049 × 10⁻⁸ C₆ = 7.71505 × 10⁻¹⁴ C₈ = 1.75760 × 10⁻¹⁸ C₁₀ =1.71383 × 10⁻²³ C₁₂ = 5.04584 × 10⁻²⁹ C₁₄ = 2.08622 × 10⁻³² 39th surfaceκ = 0 C₄ = −3.91974 × 10⁻¹¹ C₆ = 5.90682 × 10⁻¹⁴ C₈ = 2.85949 × 10⁻¹⁸C₁₀ = −1.01828 × 10⁻²² C₁₂ = 2.26543 × 10⁻²⁷ C₁₄ = −1.90645 × 10⁻³² 43rdsurface κ = 0 C₄ = 8.33324 × 10⁻⁸ C₆ = 1.42277 × 10⁻¹¹ C₈ = −1.13452 ×10⁻¹⁵ C₁₀ = 1.18459 × 10⁻¹⁸ C₁₂ = −2.83937 × 10⁻²² C₁₄ = 5.01735 × 10⁻²⁶(Values corresponding to Condition) F1 = 164.15 mm Y₀ = 17.0 mm R =20.86 mm (1)F1/Y₀ = 9.66 (2)R/Y₀ = 1.227

FIG. 6 is a diagram showing the transverse aberration in the firstexample. In the aberration diagram, Y indicates the image height, eachsolid line the center wavelength of 193.3060 nm, each dashed line193.306 nm+0.1 pm=193.3061 nm, and each chain line 193.306 nm−0.1pm=193.3059 nm. The notations in FIG. 6 also apply to FIG. 8hereinafter. As apparent from the aberration diagram of FIG. 6, thoughthe first example secures the very large image-side numerical aperture(NA=1.04) and the relatively large effective exposure region ER, thechromatic aberration is well corrected for the exposure light with thewavelength band of 193.306 nm±0.1 pm.

Second Example

FIG. 7 is an illustration showing a lens configuration of the projectionoptical system according to the second example of the presentembodiment. With reference to FIG. 7, in the projection optical systemPL according to the second example, the first imaging optical system G1is composed of the following components in order from the reticle sidealong the traveling direction of light: a biconvex lens L11 whose convexsurface of aspherical shape is kept toward the wafer; a biconvex lensL12; a negative meniscus lens L13 whose concave surface of asphericalshape is kept toward the reticle; and a first concave reflecting mirrorCM1. In the first imaging optical system G1, a reflecting surface of asecond concave reflecting mirror CM2 for reflecting the light reflectedby the first concave reflecting mirror CM1 and transmitted by thenegative meniscus lens L13, toward the second imaging optical system G2is placed in the region not including the optical axis AX between thebiconvex lens L12 and the negative meniscus lens L13. Therefore, thebiconvex lens L11 and the biconvex lens L12 constitute a first lens unithaving a positive refracting power. The first concave reflecting mirrorCM1 constitutes a concave reflecting mirror disposed near the pupilplane of the first imaging optical system G1.

On the other hand, the second imaging optical system G2 is composed ofthe following components in order from the reticle side along thetraveling direction of light: a positive meniscus lens L21 whose concavesurface is kept toward the reticle; a biconvex lens L22; a positivemeniscus lens L23 whose concave surface of aspherical shape is kepttoward the wafer; a negative meniscus lens L24 whose convex surface ofaspherical shape is kept toward the reticle; a negative meniscus lensL25 whose convex surface is kept toward the reticle; a biconcave lensL26 whose concave surface of aspherical shape is kept toward thereticle; a positive meniscus lens L27 whose concave surface is kepttoward the reticle; a negative meniscus lens L28 whose convex surface ofaspherical shape is kept toward the reticle; a biconvex lens L29; abiconvex lens L210; a positive meniscus lens L211 whose convex surfaceis kept toward the reticle; an aperture stop AS; a positive meniscuslens L212 whose concave surface is kept toward the reticle; a biconvexlens L213; a positive meniscus lens L214 whose concave surface ofaspherical shape is kept toward the wafer; a positive meniscus lens L215whose convex surface is kept toward the reticle; a positive meniscuslens L216 whose concave surface of aspherical shape is kept toward thewafer; and a planoconvex lens L217 (boundary lens Lb) whose plane iskept toward the wafer.

In the second example, a plane-parallel plate Lp is disposed in theoptical path between the planoconvex lens L217 as the boundary lens Lband the wafer W. The medium Lm consisting of deionized water is filledin the optical path between the boundary lens Lb and the plane-parallelplate Lp and in the optical path between the plane-parallel plate Lp andthe wafer W. In the second example, the transmitting members (lenses)constituting the projection optical system PL are made of silica orfluorite (CaF₂). Specifically, the lens L13, lens L216, and lens L217(Lb) are made of fluorite, and the other lenses and plane-parallel plateLp are made of silica. Namely, approximately 88% of the transmittingmembers forming the second imaging optical system G2 are made of silica.

Furthermore, in the second example all the transmitting members (lensesand plane-parallel plate) and all the reflecting members with a power(first concave reflecting mirror CM1 and second concave reflectingmirror CM2) forming the projection optical system PL are arranged alongthe single optical axis AX. In the second example, thus, the light fromthe reticle R travels through the lenses L11 to L13 to enter the firstconcave reflecting mirror CM1. The light reflected by the first concavereflecting mirror CM1 travels via the lens L13 and the second concavereflecting mirror CM2 to form an intermediate image of the reticle Rnear the first concave reflecting mirror CM1. The light reflected by thesecond concave reflecting mirror CM2 travels through the lenses L21-L217(Lb) and the plane-parallel plate Lp to form a reduced image of thereticle R on the wafer W.

In the second example, the lasing center wavelength of the ArF excimerlaser light being the exposure light is 193.306 nm, and the refractiveindex of silica near 193.306 nm varies at a rate of −1.591×10⁻⁶ perwavelength change of +1 pm and varies at a rate of +1.591×10⁻⁶ perwavelength change of −1 pm. In other words, the dispersion (dn/dλ) ofthe refractive index of silica near 193.306 nm is −1.591×10⁻⁶/pm. Therefractive index of fluorite near 193.306 nm varies at a rate of−0.980×10⁻⁶ per wavelength change of +1 pm and varies at a rate of+0.980×10⁻⁶ per wavelength change of −1 pm. In other words, thedispersion (dn/dλ) of the refractive index of fluorite near 193.306 nmis −0.980×10⁻⁶/pm.

Furthermore, the refractive index of deionized water near 193.306 nmvaries at a rate of −2.6×10⁻⁶ per wavelength change of +1 pm, and variesat a rate of +2.6×10⁻⁶ per wavelength change of −1 pm. In other words,the dispersion (dn/dλ) of the refractive index of deionized water near193.306 nm is −2.6×10⁻⁶/pm. In the second example, thus, the refractiveindex of silica for the center wavelength of 193.306 nm is 1.5603261,the refractive index of silica for 193.306 nm+0.1 pm=193.3061 nm is1.560325941, and the refractive index of silica for 193.306 nm 0.1pm=193.3059 nm is 1.560326259.

The refractive index of fluorite for the center wavelength of 193.306 nmis 1.5014548, the refractive index of fluorite for 193.306 nm+0.1pm=193.3061 nm is 1.501454702, and the refractive index of fluorite for193.306 nm−0.1 pm=193.3059 nm is 1.501454898. Furthermore, therefractive index of deionized water for the center wavelength of 193.306nm is 1.47, the refractive index of deionized water for 193.306 nm+0.1pm=193.3061 nm is 1.46999974, and the refractive index of deionizedwater for 193.306 nm−0.1 pm=193.3059 nm is 1.47000026. Table (2) belowpresents values of specifications of the projection optical system PL inthe second example.

TABLE 2 (Principal Specifications) λ = 193.306 nm β = +¼ NA = 1.04 Ro =17.0 mm Ri = 11.5 mm H = 26.0 mm D = 4.0 mm R = 20.86 mm Y₀ = 17.0 mm(Specifications of Optical Members) Surface Number r d n Optical member(reticle surface) 72.14497  1 295.66131 46.03088 1.5603261 (L11)  2*−228.07826 1.02581  3 847.63618 40.34103 1.5603261 (L12)  4 −207.90948124.65407  5* −154.57886 13.00000 1.5014548 (L13)  6 −667.19164 9.58580 7 −209.52775 −9.58580 (CM1)  8 −667.19164 −13.00000 1.5014548 (L13)  9*−154.57886 −109.65407 10 2517.52751 147.23986 (CM2) 11 −357.7131841.75496 1.5603261 (L21) 12 −196.81705 1.00000 13 8379.53651 40.000001.5603261 (L22) 14 −454.81020 8.23083 15 206.30063 58.07852 1.5603261(L23) 16* 367.14898 24.95516 17* 258.66863 20.00000 1.5603261 (L24) 18272.27694 274.16477 19 671.42370 49.62123 1.5603261 (L25) 20 225.7990735.51978 21* −283.63484 15.10751 1.5603261 (L26) 22 261.37852 56.7182223 −1947.68869 54.63076 1.5603261 (L27) 24 −227.05849 5.77639 25*788.97953 15.54026 1.5603261 (L28) 26 460.12935 18.83954 27 1925.7503856.54051 1.5603261 (L29) 28 −295.06884 1.00000 29 861.21046 52.505151.5603261 (L210) 30 −34592.86759 1.00000 31 614.86639 37.34179 1.5603261(L211) 32 39181.66426 1.00000 33 ∞ 46.27520 (AS) 34 −11881.9185430.00000 1.5603261 (L212) 35 −631.95129 1.00000 36 1465.88641 39.891131.5603261 (L213) 37 −542.10144 1.00000 38 336.45791 34.80369 1.5603261(L214) 39* 2692.15238 1.00000 40 112.42843 43.53915 1.5603261 (L215) 41189.75478 1.00000 42 149.91358 42.41577 1.5014548 (L216) 43* 107.288881.06533 44 90.28791 31.06087 1.5014548 (L217:Lb) 45 ∞ 1.00000 1.47 (Lm)46 ∞ 3.00000 1.5603261 (Lp) 47 ∞ 5.00000 1.47 (Lm) (wafer surface)(Aspherical data) 2nd surface κ = 0 C₄ = 9.57585 × 10⁻⁹ C₆ = 7.09690 ×10⁻¹³ C₈ = 1.30845 × 10⁻¹⁶ C₁₀ = −5.52152 × 10⁻²² C₁₂ = 4.46914 × 10⁻²⁵C₁₄ = −2.07483 × 10⁻²⁹ 5th surface and 9th surface (same surface) κ = 0C₄ = 1.16631 × 10⁻⁸ C₆ = 6.70616 × 10⁻¹³ C₈ = −1.87976 × 10⁻¹⁷ C₁₀ =1.71587 × 10⁻²⁰ C₁₂ = −2.34827 × 10⁻²⁴ C₁₄ = 1.90285 × 10⁻²⁸ 16thsurface κ = 0 C₄ = −4.06017 × 10⁻⁸ C₆ = 2.22513 × 10⁻¹² C₈ = −9.05000 ×10⁻¹⁷ C₁₀ = 3.29839 × 10⁻²¹ C₁₂ = −7.46596 × 10⁻²⁶ C₁₄ = 1.06948 × 10⁻³⁰17th surface κ = 0 C₄ = −6.69592 × 10⁻⁸ C₆ = 1.42455 × 10⁻¹² C₈ =−5.65516 × 10⁻¹⁷ C₁₀ = 2.48078 × 10⁻²¹ C₁₂ = −2.91653 × 10⁻²⁶ C₁₄ =1.53981 × 10⁻³¹ 21st surface κ = 0 C₄ = −7.97186 × 10⁻⁸ C₆ = −1.32969 ×10⁻¹² C₈ = −1.98377 × 10⁻¹⁷ C₁₀ = −4.95016 × 10⁻²¹ C₁₂ = 2.53886 × 10⁻²⁵C₁₄ = −4.16817 × 10⁻²⁹ 25th surface κ = 0 C₄ = −1.55844 × 10⁻⁸ C₆ =7.27672 × 10⁻¹⁴ C₈ = 1.90600 × 10⁻¹⁸ C₁₀ = 1.21465 × 10⁻²³ C₁₂ =−7.56829 × 10⁻²⁹ C₁₄ = 1.86889 × 10⁻³² 39th surface κ = 0 C₄ = −6.91993× 10⁻¹¹ C₆ = 7.80595 × 10⁻¹⁴ C₈ = 3.31216 × 10⁻¹⁸ C₁₀ = −1.39159 × 10⁻²²C₁₂ = 3.69991 × 10⁻²⁷ C₁₄ = −4.01347 × 10⁻³² 43rd surface κ = 0 C₄ =8.30019 × 10⁻⁸ C₆ = 1.24781 × 10⁻¹¹ C₈ = −9.26768 × 10⁻¹⁶ C₁₀ = 1.08933× 10⁻¹⁸ C₁₂ = −3.01514 × 10⁻²² C₁₄ = 5.41882 × 10⁻²⁶ (Valuescorresponding to Condition) F1 = 178.98 mm Y₀ = 17.0 mm R = 20.86 mm(1)F1/Y₀ = 10.53 (2)R/Y₀ = 1.227

FIG. 8 is a diagram showing the transverse aberration in the secondexample. It is also apparent from the aberration diagram of FIG. 8, aswas the case with the first example, that the second example alsosecures the very large image-side numerical aperture (NA=1.04) and therelatively large effective exposure region ER, while the chromaticaberration is well corrected for the exposure light with the wavelengthband of 193.306 nm±0.1 pm.

In each example, as described above, the high image-side numericalaperture of 1.04 is secured for the ArF excimer laser light with thewavelength of 193.306 nm, and the effective exposure region (stillexposure region) of arcuate shape of 26.0 mm×4.0 mm can be secured;therefore, the scanning exposure of the circuit pattern can be performedat high resolution within the exposure region of rectangular shape of 26mm×33 mm, for example.

Next, the third example of the embodiment will be described. FIG. 9 isan illustration showing a lens configuration of the catadioptricprojection optical system according to the third example of theembodiment. The catadioptric projection optical system PL1 according tothe third example is composed of the following optical systems in orderfrom the object side (i.e., the reticle R1 side): a first imagingoptical system G1 for forming an intermediate image of the reticle R1located on the first surface; and a second imaging optical system G2 forforming an intermediate image of the reticle R1 on a wafer (not shown)located on the second surface.

The first imaging optical system G1 is composed of a lens unit with apositive refracting power (fourth lens unit or first unit) G11,after-described lens L5, and two reflecting mirrors M1, M2. The lensunit G11 functions for making the optical system telecentric on thereticle R1 side. The second imaging optical system G2 is composed ofafter-described two reflecting mirrors M3, M4, a lens unit with anegative refracting power (first lens unit or third unit) G21, a lensunit with a positive refracting power (second lens unit) G22, anaperture stop AS1, and a lens unit with a positive refracting power(third lens unit) G23. The lens unit G21 functions to adjust themagnification and to relieve the variation due to the difference offield angles of the beam expanded by the reflecting mirror M3, so as tosuppress occurrence of aberration. The lens unit G22 functions toconverge the diverging beam. The lens unit G23 functions to condense thebeam so as to achieve the large numerical aperture on the wafer side.

Here the lens unit G11 is composed of the following components in orderof passage of rays from the object side (reticle R1 side): aplane-parallel plate L1; a negative meniscus lens L2 whose concavesurface of aspherical shape is kept toward the object side; a biconvexlens L3; and a positive meniscus lens L4 whose concave surface ofaspherical shape is kept toward the wafer.

The beam transmitted by the positive meniscus lens L4 travels throughthe negative meniscus lens (negative lens) L5 with the concave surfacekept toward the object, is reflected by the concave reflecting mirror(concave mirror or first reflecting mirror) M1 with the concave surfacekept toward the object, passes again through the negative meniscus lensL5, and is reflected by the convex reflecting mirror (optical pathseparating mirror or second reflecting mirror) M2 with the convexsurface kept toward the wafer. The negative meniscus lens L5 functionsfor satisfying the Petzval's condition.

The beam reflected by the convex reflecting mirror M2 forms anintermediate image of the reticle R1 at the position a shown in FIG. 9,in order to securely achieve the optical path separation between thebeam toward the reticle R1 and the beam toward the wafer. Here theposition a is located on or near a plane whose normal is the opticalaxis AX1 where the concave reflecting mirror M1 is placed.

Next, the beam reflected by the convex reflecting mirror M2 is incidentto the concave reflecting mirror (first field mirror or third reflectingmirror) M3 with the concave surface kept toward the object, to be bentinto a direction toward the optical axis AX1 of the catadioptricprojection optical system PL1, and is outputted from the concavereflecting mirror M3. The beam emerging from the concave reflectingmirror M3 is quickly converged, is reflected by the convex reflectingmirror (second field mirror or fourth reflecting mirror) M4 with theconvex surface kept toward the wafer, and is directly incident to thenegative meniscus lens L6 forming the lens unit G21. The convexreflecting mirror M4 relieves the variation of the beam due to fieldangles expanded by the concave reflecting mirror M3, so as to suppressoccurrence of aberration. The negative meniscus lens L5, concavereflecting mirror M1, convex reflecting mirror M2, concave reflectingmirror M3, and convex reflecting mirror M4 constitute a second unit.

The lens unit G21 is composed of the following components in order ofpassage of rays: a negative meniscus lens L6 whose convex surface ofaspherical shape is kept toward the object; and a biconcave lens L7whose concave surface of aspherical shape is kept toward the wafer.Since the negative meniscus lens L6 and the biconcave lens L7 have thelens surfaces of aspherical shape, good imaging performance can beachieved throughout the entire region in the exposure area, whilesecuring the large numerical aperture on the image side of thecatadioptric projection optical system PL1. The lens unit G22 iscomposed of the following components in order of passage of rays: apositive meniscus lens L8 whose concave surface of aspherical shape iskept toward the object; a biconvex lens L9; a positive meniscus lens L10whose concave surface of aspherical shape is kept toward the object; abiconvex lens L11; and a biconvex lens L12. The lens unit G23 iscomposed of the following components in order of passage of rays: apositive meniscus lens L13 whose convex surface is kept toward theobject; a positive meniscus lens L14 whose convex surface is kept towardthe object; a positive meniscus lens L15 whose convex surface is kepttoward the object; a positive meniscus lens L16 whose concave surface ofaspherical shape is kept toward the wafer; a positive meniscus lens L17whose concave surface of aspherical shape is kept toward the wafer; anda planoconvex lens L18 with a positive refracting power whose convexsurface is kept toward the object. The lens unit G22, aperture stop AS1,and lens unit G23 constitute a fourth unit.

The catadioptric projection optical system PL1 is constructed to satisfythe condition of 0.17<Ma/L<0.6, where Ma is a distance on the opticalaxis AX1 between the reflecting mirror M3 and the aperture stop AS1, andL a distance between the reticle R1 and the wafer. When Ma/L satisfiesthe lower limit, it is feasible to avoid mechanical interference of theconcave reflecting mirror M3 with the lens unit G21 and the lens unitG22. When Ma/L satisfies the upper limit, it is feasible to avoid anincrease in the total length and an increase in the size of thecatadioptric projection optical system PL1. For securely avoiding themechanical interference and securely avoiding the increase in the totallength and the increase in the size of the projection optical system,the projection optical system is further preferably constructed tosatisfy the condition of 0.2<Ma/L<0.5.

When this catadioptric projection optical system PL1 of the presentexample is applied to the exposure apparatus, pure water with therefractive index of about 1.4 is interposed in the optical path betweenthe lens L18 and the wafer, where the refractive index of the atmospherein the catadioptric projection optical system PL1 is 1. Therefore, thewavelength of the exposure light in pure water is about 0.71 (1/1.4)times that in the atmosphere, whereby the resolution can be enhanced.

The optical axis AX1 of every optical element included in thecatadioptric projection optical system PL1 and having the predeterminedrefracting power is placed substantially on the single straight line,and the region of the image formed on the wafer by the catadioptricprojection optical system PL1 is the off-axis region not including theoptical axis AX1. Therefore, it is feasible to reduce the degree ofdifficulty of production in production of the catadioptric projectionoptical system PL1 and to readily achieve relative adjustment of eachoptical member.

In the catadioptric projection optical system PL1 of the third example,since the intermediate image of the reticle R1 is formed in the firstimaging optical system G1, it is feasible to readily and securelyachieve the optical path separation between the beam toward the reticleR1 and the beam toward the wafer, even in the case where the numericalapertures of the catadioptric projection optical system PL1 areincreased. Since the second imaging optical system G2 has the lens unitG21 with the negative refracting power, it is feasible to shorten thetotal length of the catadioptric projection optical system PL1 and toreadily achieve the adjustment for satisfying the Petzval's condition.Furthermore, the lens unit G21 relieves the variation due to thedifference of field angles of the beam expanded by the concavereflecting mirror M3, so as to suppress occurrence of aberration.Therefore, good imaging performance can be achieved throughout theentire region in the exposure area, even in the case where the reticleR1-side and wafer-side numerical apertures of the catadioptricprojection optical system PL1 are increased in order to enhance theresolution.

Next, the fourth example of the embodiment will be described withreference to the drawing. FIG. 10 is an illustration showing a lensconfiguration of the catadioptric projection optical system according tothe fourth example of the embodiment. The catadioptric projectionoptical system PL2 of the fourth example is composed of the followingoptical systems in order from the object side (i.e., the reticle R2side): a first imaging optical system G3 for forming an intermediateimage of reticle R2 located on the first surface; and a second imagingoptical system G4 for forming an intermediate image of the reticle R2 ona wafer (not shown) located on the second surface.

The first imaging optical system G3 is composed of a lens unit with apositive refracting power (fourth lens unit or first unit) G31,after-described lens L24, and two reflecting mirrors M21, M22. The lensunit G31 functions for making the optical system telecentric on thereticle R2 side. The second imaging optical system G4 is composed ofafter-described two reflecting mirrors M23, M24, a lens unit with anegative refracting power (first lens unit or third unit) G41, a lensunit with a positive refracting power (second lens unit) G42, anaperture stop AS2, and a lens unit with a positive refracting power(third lens unit) G43. The lens unit G41 functions to adjust themagnification and to relieve the variation due to the difference offield angles of the beam expanded by the reflecting mirror M23, so as tosuppress occurrence of aberration. The lens unit G42 functions toconverge the diverging beam. The lens unit G43 condenses the beam so asto achieve a large numerical aperture on the wafer side.

Here the lens unit G31 is composed of the following components in orderof passage of rays from the object side (reticle R2 side): aplane-parallel plate L21; a positive meniscus lens L22 whose concavesurface of aspherical shape is kept toward the object; and a biconvexlens L23. The beam transmitted by the biconvex lens L23 passes throughthe negative meniscus lens (negative lens) L24 with the concave surfacekept toward the object, is reflected by the concave reflecting mirror(concave reflecting mirror or first reflecting mirror) M21 with theconcave surface of aspherical shape kept toward the object, passes againthrough the negative meniscus lens L24, and is then reflected by theconvex reflecting mirror (optical path separating mirror or secondreflecting mirror) M22 with the convex surface of aspherical shape kepttoward the wafer. The negative meniscus lens L24 functions forsatisfying the Petzval's condition.

The beam reflected by the convex reflecting mirror M22 forms anintermediate image of the reticle R2 at the position b shown in FIG. 10,in order to securely achieve the optical path separation between thebeam toward the reticle R2 and the beam toward the wafer. Here theposition b is located on or near a plane whose normal is the opticalaxis AX2 where the concave reflecting mirror M21 is placed.

Next, the beam reflected by the convex reflecting mirror M22 is incidentto the concave reflecting mirror (first field mirror or third reflectingmirror) M23 with the concave surface kept toward the object, to be bentinto a direction toward the optical axis AX2 of the catadioptricprojection optical system PL2, and is reflected by the concavereflecting mirror M23. The beam reflected by the concave reflectingmirror M23 is quickly converged, is reflected by the convex reflectingmirror (second field mirror or fourth reflecting mirror) M24 with theconvex surface of aspherical shape kept toward the wafer, and isdirectly incident to the biconcave lens L25 forming the lens unit G41.The convex reflecting mirror M24 relieves the variation of the beam dueto the field angles expanded by the concave reflecting mirror M23, so asto suppress occurrence of aberration. The negative meniscus lens L24,concave reflecting mirror M21, convex reflecting mirror M22, concavereflecting mirror M23, and convex reflecting mirror M24 constitute asecond unit.

The lens unit G41 is composed of the following components in order ofpassage of rays: a biconcave lens L25 whose concave surface ofaspherical shape is kept toward the object; and a biconcave lens L26whose concave surface of aspherical shape is kept toward the wafer.Since the biconcave lens L25 and the biconcave lens L26 have the lenssurfaces of aspherical shape, it is feasible to achieve good imagingperformance throughout the entire region in the exposure area, whileachieving the large numerical aperture on the image side of thecatadioptric projection optical system PL2.

The lens unit G42 is composed of the following components in order ofpassage of rays: a biconvex lens L27 whose convex surface of asphericalshape is kept toward the object; a negative meniscus lens L28 whoseconvex surface is kept toward the object; a positive meniscus lens L29whose concave surface is kept toward the object; and a negative meniscuslens L30 whose convex surface of aspherical shape is kept toward thewafer. The lens unit G43 is composed of the following components inorder of passage of rays: a positive meniscus lens L31 whose convexsurface is kept toward the object; a positive meniscus lens L32 whoseconvex surface is kept toward the object; a positive meniscus lens L33whose convex surface is kept toward the object; a positive meniscus lensL34 whose concave surface of aspherical shape is kept toward the wafer;a positive meniscus lens L35 whose concave surface of aspherical shapeis kept toward the wafer; and a planoconvex lens L36 whose convexsurface is kept toward the object. The lens unit G42, aperture stop AS2,and lens unit G43 constitute a fourth unit.

The catadioptric projection optical system PL2 is constructed so as tosatisfy the condition of 0.17<M2a/L2<0.6, where M2 is a distance on theoptical axis AX2 between the reflecting mirror M23 and the aperture stopAS2, and L2 the distance between the reticle R2 and the wafer. WhenM2a/L2 satisfies the lower limit, it is feasible to avoid mechanicalinterference of the concave reflecting mirror M23 with the lens unit G41and the lens unit G42. When M2a/L2 satisfies the upper limit, it isfeasible to avoid an increase in the total length and an increase in thesize of the catadioptric projection optical system PL2. For securelyavoiding the mechanical interference and securely avoiding the increasein the total length and the increase in the size of the projectionoptical system, the projection optical system is more preferablyconstructed to satisfy the condition of 0.5<M2a/L2<0.2.

When the catadioptric projection optical system PL2 of this example isapplied to the exposure apparatus, pure water having the refractiveindex of about 1.4 is interposed in the optical path between the lensL36 and the wafer, where the refractive index of the atmosphere in thecatadioptric projection optical system PL2 is 1. Therefore, thewavelength of the exposure light in pure water becomes about 0.71(1/1.4) times that in the atmosphere, whereby the resolution can beenhanced.

The optical axis AX2 of every optical element included in thecatadioptric projection optical system PL2 and having the predeterminedrefracting power is placed substantially on the single straight line,and the region of the image formed on the wafer by the catadioptricprojection optical system PL2 is the off-axis region not including theoptical axis AX2. Therefore, it is feasible to reduce the degree ofdifficulty of production in production of the catadioptric projectionoptical system PL2 and to readily achieve relative adjustment of eachoptical member.

Since the catadioptric projection optical system PL2 of the fourthexample forms the intermediate image of the reticle R2 in the firstimaging optical system G3, the optical path separation can be readilyand securely achieved between the beam toward the reticle R2 and thebeam toward the wafer, even in the case where the numerical apertures ofthe catadioptric projection optical system PL2 are increased. Since thesecond imaging optical system G4 has the lens unit G41 with the negativerefracting power, it is feasible to shorten the total length of thecatadioptric projection optical system PL2 and to readily achieve theadjustment for satisfying the Petzval's condition. Furthermore, the lensunit G41 relieves the variation due to the difference of field angles ofthe beam expanded by the concave reflecting mirror M23, so as tosuppress occurrence of aberration. Therefore, good imaging performancecan be achieved throughout the entire region in the exposure area, evenin the case where the reticle R2-side and wafer-side numerical aperturesof the catadioptric projection optical system PL2 are increased in orderto enhance the resolution.

The catadioptric projection optical system PL1 of the third exampledescribed above is arranged so that the light reflected by the convexreflecting mirror M4 is incident to the lens unit G21, but the opticalsystem may also be arranged so that a double pass lens is disposedbetween the convex reflecting mirror M4 and the lens unit G21. In thiscase, the light reflected by the concave reflecting mirror M3 passesthrough the double pass lens, is reflected by the convex reflectingmirror M4, passes again through the double pass lens, and then entersthe lens unit G21. Similarly, the catadioptric projection optical systemPL2 of the fourth example is arranged so that the light reflected by theconvex reflecting mirror M24 is incident to the lens unit G41, but theoptical system may also be arranged so that a double pass lens isdisposed between the convex reflecting mirror M24 and the lens unit G41.

In the catadioptric projection optical systems PL1, PL2 of therespective examples described above, pure water was interposed betweenthe lens located nearest to the wafer, and the wafer, and it is alsopossible to adopt a configuration wherein another medium having arefractive index larger than 1.1 is interposed, where the refractiveindex of the atmosphere in the catadioptric projection optical systemPL1 or PL2 is 1.

Presented below are values of specifications of the catadioptricprojection optical system PL1 according to the third example. In thespecifications, as shown in FIG. 11, A represents a radius of a portionwhere the exposure light is blocked by the optical elements constitutingthe catadioptric projection optical system PL1, with the center on theoptical axis AX1 of the catadioptric projection optical system PL1, B aradius of the maximum image height with the center on the optical axisAX1 of the catadioptric projection optical system PL1, H a length alongthe Y-direction of the effective exposure region, and C a length alongthe X-direction of the effective exposure region. In the specifications,NA represents the numerical aperture, d the surface separation, n therefractive index, and λ the center wavelength. Furthermore, in thespecifications M represents the distance on the optical axis AX1 betweenthe reflecting mirror M3 and the unrepresented wafer, and L the distancebetween the reticle R1 and the wafer.

Table 3 presents the specifications of the optical members of thecatadioptric projection optical system PL1 according to the thirdexample. In the specifications of the optical members in Table 3, eachsurface number in the first column indicates an order of a surface alongthe traveling direction of rays from the object side, the second columna radius of curvature of each surface (mm), the third column an on-axisspacing or surface separation (mm) of each surface, and the fourthcolumn a glass material of each optical member.

Table 4 presents the aspherical coefficients of the lenses with a lenssurface of aspherical shape and the reflecting mirrors used in thecatadioptric projection optical system PL1 in the third example. In theaspherical coefficients of Table 4, aspherical surface numbers in thefirst column correspond to the surface numbers in the specifications ofthe optical members in Table 1. The second column represents thecurvature of each aspherical surface (1/mm), the third column theconical coefficient k and the 12th-order aspherical coefficient, thefourth column the 4th-order and 14th-order aspherical coefficients, thefifth column the 6th-order and 16th-order aspherical coefficients, thesixth column the 8th-order and 18th-order aspherical coefficients, andthe seventh column the 10th-order and 20th-order asphericalcoefficients.

In the third and fourth examples, each aspherical surface is expressedby the aforementioned Eq (a).

Third Example Specifications

Image-side NA: 1.20

Exposure area: A=14 mm B=18 mm

-   -   H=26.0 mm C=4 mm

Imaging magnification: ¼

Center wavelength: 193.306 nm

Refractive index of silica: 1.5603261

Refractive index of fluorite: 1.5014548

Refractive index of liquid 1: 1.43664

Dispersion of silica (dn/dλ): −1.591E-6/pm

Dispersion of fluorite (dn/dλ): −0.980E-6/pm

Dispersion of liquid 1 (dn/dλ): −2.6E-6/pm

Values corresponding to Condition Ma=374.65 mm L=1400 mm

TABLE 3 (Specifications of Optical Members) #2 #3 #4 #1 ∞ 50.0000  1: ∞8.0000 #5  2: ∞ 33.0000  3: ASP1 25.0422 #5  4: −163.96521 1.0000  5:355.31617 60.7391 #5  6: −261.84115 1.0000  7: 277.33354 29.0109 #5  8:ASP2 224.5285  9: −176.61872 20.0000 #5 10: −515.60710 10.4614 11: ASP3−10.4614 #6 12: −515.60710 −20.0000 #5 13: −176.61872 −204.5285 14: ASP4518.3706 #6 15: −517.39842 −241.3807 #6 16: −652.07494 171.3807 #6 17:ASP5 20.0000 #5 18: 171.59382 41.4743 19: −245.94525 20.0000 #5 20: ASP695.1415 21: ASP7 28.3218 #5 22: −273.72261 1.0000 23: 578.31684 49.6079#5 24: −908.96420 1.0000 25: ASP8 23.1140 #5 26: −713.30127 1.0000 27:1494.96847 33.6453 #5 28: −1392.26668 100.2723 29: 1382.10341 24.7691 #530: −2944133.03600 5.3079 31: ∞ 6.0869 #7 32: 596.90080 37.1298 #5 33:524859.29548 1.0000 34: 367.83725 41.0495 #5 35: 1341.09674 1.0000 36:180.61255 61.4605 #5 37: 464.28786 1.0000 38: 125.76761 49.2685 #5 39:ASP9 1.0000 40: 89.27467 40.3615 #5 41: ASP10 1.1254 42: 79.3545137.7011 #5 43: ∞ 1.0000 #8 #9 ∞ #1: 1st surface #2: Radius of curvature#3: Surface spacing #4: Medium #5: silica glass #6: reflecting mirror#7: aperture stop #8: pure water #9: 2nd surface

TABLE 4 (Aspherical Coefficients) k c4 c6 c8 c10 #12 #13 c12 c14 c16 c18c20 ASP1 −0.00714775 0.00000E+00 3.70121E−08 4.46586E−13 1.04583E−176.67573E−21 −5.81072E−25 5.12689E−29 0.00000E+00 0.00000E+00 0.00000E+00ASP2 0.00091632 0.00000E+00 2.33442E−08 −7.41117E−13 5.06507E−17−4.32871E−21 1.56850E−25 −1.33250E−30 0.00000E+00 0.00000E+000.00000E+00 ASP3 −0.00346903 0.00000E+00 −1.67447E−09 −6.49516E−14−5.93050E−19 −8.10217E−23 3.21506E−27 −6.92598E−32 0.00000E+000.00000E+00 0.00000E+00 ASP4 −0.00078630 0.00000E+00 3.06927E−104.69465E−14 −6.39759E−19 2.45900E−23 −8.28832E−28 1.58122E−320.00000E+00 0.00000E+00 0.00000E+00 ASP5 0.00125662 0.00000E+001.03544E−08 −1.28243E−12 −3.97225E−17 −8.03173E−21 3.90718E−251.64002E−30 0.00000E+00 0.00000E+00 0.00000E+00 ASP6 0.005076340.00000E+00 1.00543E−08 −3.32807E−12 −1.38706E−17 2.64276E−211.41136E−25 −6.70516E−30 0.00000E+00 0.00000E+00 0.00000E+00 ASP7−0.00253727 0.00000E+00 −3.94919E−10 9.50312E−14 −1.02153E−18−1.22660E−22 3.11154E−27 −4.99394E−31 0.00000E+00 0.00000E+000.00000E+00 ASP8 −0.00025661 0.00000E+00 −9.13443E−09 −8.61174E−144.52406E−19 −2.29061E−23 5.86934E−28 −7.10478E−33 0.00000E+000.00000E+00 0.00000E+00 ASP9 0.00458263 0.00000E+00 2.66745E−08−3.15468E−13 7.16318E−17 1.41053E−21 −2.22512E−25 1.68093E−290.00000E+00 0.00000E+00 0.00000E+00 ASP10 0.01117107 0.00000E+002.45701E−07 4.19793E−11 4.83523E−15 2.02242E−18 −1.59072E−22 1.41579E−250.00000E+00 0.00000E+00 0.00000E+00 #12: Aspherical surface number #13:Curvature

FIG. 12 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system PL1 according to the presentexample. In FIG. 12, Y indicates the image height, each dashed line thetransverse aberration at the wavelength of 193.3063 nm, each solid linethe transverse aberration at the wavelength of 193.3060 nm, and eachchain line the transverse aberration at the wavelength of 193.3057 nm.As shown in the transverse aberration diagram of FIG. 12, thecatadioptric projection optical system PL1 of the present example hasthe large numerical aperture and is corrected in a good balance foraberration throughout the entire exposure area though it has no largeoptical element.

The values of specifications of the catadioptric projection opticalsystem PL2 according to the fourth example will be presented below.Table 5 presents the specifications of the optical members of thecatadioptric projection optical system PL2 in the fourth example. Table6 presents the aspherical coefficients of the lenses with a lens surfaceof aspherical shape and the reflecting mirrors used in the catadioptricprojection optical system PL2 according to the fourth example. Thespecifications, the specifications of the optical members, and theaspherical coefficients will be described with use of the same referencesymbols as those used in the description of the specifications of thecatadioptric projection optical system PL1 in the third example.

Fourth Example Specifications

Image-side NA: 1.20

Exposure area: A=13.5 mm B=17.5 mm

H=26.0 mm C=4 mm

Imaging magnification: ⅕

Center wavelength: 193.306 nm

Refractive index of silica: 1.5603261

Refractive index of fluorite: 1.5014548

Refractive index of liquid 1: 1.43664

Dispersion of silica (dn/dλ): −1.591E-6/pm

Dispersion of fluorite (dn/dλ): −0.980E-6/pm

Dispersion of liquid 1 (dn/dλ): −2.6E-6/pm

Values corresponding to Condition Ma=424.85 mm L=1400 mm

TABLE 5 (Specifications of Optical Members) #2 #3 #4 #1 ∞ 74.5841  1: ∞8.0000 #5  2: ∞ 33.0000  3: ASP1 22.9375 #5  4: −238.83712 1.0000  5:226.68450 59.5357 #5  6: −908.69406 202.7480 #6  7: −165.20501 20.0000#5  8: −669.93146 45.4417  9: ASP2 −45.4417 #6 10: −669.93146 −20.0000#5 11: −165.20501 −182.7480 12: ASP3 476.5531 #6 13: −410.99944−182.7518 #6 14: ASP4 164.9642 #6 15: ASP5 28.4827 #5 16: 239.4549538.2383 17: −497.63245 20.0000 #5 18: ASP6 89.6638 19: ASP7 48.7904 #520: −290.43245 1.0000 21: 1036.93127 60.0000 #5 22: 1015.63994 19.728523: −2533.07822 63.4343 #5 24: −278.02969 31.4485 25: −1388.3682440.8485 #5 26: ASP8 1.0000 27: ∞ 1.0000 #7 28: 479.05778 35.6437 #5 29:1637.29836 1.0000 30: 329.32813 44.1312 #5 31: 1053.37530 1.0000 32:200.35146 57.3982 #5 33: 515.50441 1.0000 34: 118.38756 60.5521 #5 35:ASP9 1.0000 36: 81.03425 37.8815 #14 37: ASP10 1.0000 38: 81.7193235.7388 #14 39: ∞ 1.0000 #8 #9 ∞ #1: 1st surface #2: Radius of curvature#3: Surface spacing #4: Medium #5: silica glass #6: reflecting mirror#7: aperture stop #8: pure water #9: 2nd surface #14: Fluorite

TABLE 6 (Aspherical Coefficients) k c4 c6 c8 c10 #12 #13 c12 c14 c16 c18c20 ASP1 −0.00388454 0.00000E+00 2.22245E−08 1.47956E−13 −1.47977E−171.83827E−21 −3.79672E−26 6.22409E−31 0.00000E+00 0.00000E+00 0.00000E+00ASP2 −0.00372368 0.00000E+00 −1.37639E−09 −9.27463E−14 −2.38568E−18−4.78730E−22 4.14849E−26 −2.22906E−30 0.00000E+00 0.00000E+000.00000E+00 ASP3 −0.00090790 0.00000E+00 −4.17158E−09 1.53090E−13−4.47592E−18 4.88099E−22 −2.64998E−26 6.12220E−31 0.00000E+000.00000E+00 0.00000E+00 ASP4 −0.00254948 0.00000E+00 1.56073E−091.95837E−14 1.84638E−18 −8.80727E−23 1.81493E−27 −1.48191E−320.00000E−00 0.00000E+00 0.00000E+00 ASP5 −0.00102929 0.00000E+00−3.82817E−11 1.56504E−13 −2.89929E−16 1.68400E−20 −5.96465E−251.20191E−29 0.00000E−00 0.00000E+00 0.00000E+00 ASP6 0.005411540.00000E+00 3.81649E−08 −1.10034E−12 −3.69090E−16 1.33858E−206.34523E−25 −3.45549E−29 0.00000E+00 0.00000E+00 0.00000E+00 ASP70.00102903 0.00000E+00 −3.14004E−08 2.87908E−13 −1.32597E−17 2.02315E−22−5.49818E−27 −4.97090E−32 0.00000E+00 0.00000E+00 0.00000E+00 ASP8−0.00012579 0.00000E+00 −5.21260E−09 −2.97679E−14 −4.97667E−191.15081E−23 −9.40202E−29 5.04787E−34 0.00000E−00 0.00000E+00 0.00000E+00ASP9 0.00403277 0.00000E+00 4.99776E−08 −8.99272E−13 6.60787E−174.38434E−22 −4.24581E−26 4.81058E−30 0.00000E−00 0.00000E+00 0.00000E+00ASP10 0.01060914 0.00000E+00 2.60785E−07 4.78050E−11 5.21548E−151.26891E−18 1.53552E−22 4.32477E−26 0.00000E−00 0.00000E+00 0.00000E+00#12: Aspherical surface number #13: Curvature

FIG. 13 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system PL2 according to the presentexample. In FIG. 13, Y indicates the image height, each dashed line thetransverse aberration at the wavelength of 1933063 nm, each solid linethe transverse aberration at the wavelength of 193.3060, and each chainline the transverse aberration at the wavelength of 193.3057 nm. Asshown in the transverse aberration diagram of FIG. 13, the catadioptricprojection optical system PL2 of the present example has the largenumerical aperture and is corrected in a good balance for aberrationthroughout the entire exposure area though it has no large opticalelement.

The fifth example of the embodiment will be described below withreference to the drawing. FIG. 14 is an illustration showing a lensconfiguration of the catadioptric projection optical system according tothe fifth example of the embodiment. The catadioptric projection opticalsystem PL1 of the fifth example is comprised of the following opticalsystems in order from the object side (i.e., the reticle R1 side): afirst imaging optical system G1 for forming a first intermediate imageand a second intermediate image of the reticle R1 located on the firstsurface; and a second imaging optical system G2 for relaying the secondintermediate image of the reticle R1 onto a wafer (not shown) located onthe second surface.

The first imaging optical system G1 is composed of a lens unit with apositive refracting power (field lens unit) G11, and after-described sixreflecting mirrors M1-M6. The lens unit G11 functions to correct fordistortion and others and to make the optical system telecentric on thereticle R1 side. The lens unit G11 functions to keep the size of theimage of the reticle R1 unchanged even if the reticle R1 is placed withdeviation from the desired position in the direction of the optical axisAX1; therefore, the performance of the catadioptric projection opticalsystem PL1 can be maintained high.

The second imaging optical system G2 is entirely composed oftransmitting optical elements and is composed of a lens unit with apositive refracting power (first lens unit) G21, a lens unit with anegative refracting power (second lens unit) G22, a lens unit with apositive refracting power (third lens unit) G23, an aperture stop AS1,and a lens unit with a positive refracting power (fourth lens unit) G24.Since the second imaging optical system G2 is entirely composed of thetransmitting optical elements, it is free of the optical path separationload; therefore, the image-side numerical aperture of the catadioptricprojection optical system PL1 can be set large and a reduced image canbe formed at a high reduction rate on the wafer located on the secondsurface. The lens units G21-G24 advantageously function for satisfyingthe Petzval's condition. The configuration of the lens units G21-G24 isable to avoid an increase in the total length of the catadioptricprojection optical system PL1. The lens units G21-G23 are effective tocorrection for various aberrations such as coma.

Here the lens unit G11 is composed of the following components in orderof passage of rays from the object side (reticle R1 side): aplane-parallel plate L1; a positive meniscus lens L2 whose concavesurface of aspherical shape is kept toward the object; a biconvex lensL3; and a biconvex lens L4. The beam transmitted by the biconvex lens L4is reflected by the concave reflecting mirror M1 whose concave surfaceof aspherical shape is kept toward the object, the convex reflectingmirror M2 whose convex surface of aspherical shape is kept toward thewafer, and the concave reflecting mirror M3 whose concave surface iskept toward the object, to form the first intermediate image. The beamreflected by the reflecting mirror M3 is reflected by the convexreflecting mirror M4 whose convex surface is kept toward the wafer, theconcave reflecting mirror M5 whose concave surface of aspherical shapeis kept toward the object, and the concave reflecting mirror M6 whoseconcave surface is kept toward the wafer.

Since the beam is continuously reflected by the reflecting mirrors M1-M6without intervention of any lens, the Petzval's condition can be readilymet by adjustment of each reflecting mirror M1-M6. A region for holdingeach reflecting mirror M1-M6 can be secured and it is easy to hold eachreflecting mirror M1-M6. The curvature of field can be readily correctedfor by changing the radius of curvature of each reflecting mirror M1-M6.The beam reflected by the reflecting mirror M6 forms the secondintermediate image.

In this case, the concave reflecting mirror M3 is placed at the positionmost distant from the optical axis AX1 and the beam can be focused bythis concave reflecting mirror M3; therefore, the beam can be setlargely apart from the optical axis AX1 of the catadioptric projectionoptical system PL1, without intervention of any lens between thereflecting mirrors M1-M6, whereby interference can be avoided betweenbeams. When the beam is continuously reflected by the four reflectingmirrors M3-M6, it is feasible to avoid an increase in the total lengthof the catadioptric projection optical system PL1.

The lens unit G21 is composed of the following components in order ofpassage of rays: a positive meniscus lens L5 whose convex surface iskept toward the object; a positive meniscus lens L6 whose concavesurface of aspherical shape is kept toward the wafer; a positivemeniscus lens L7 whose convex surface is kept toward the object; anegative meniscus lens L8 whose convex surface is kept toward theobject; and a negative meniscus lens L9 whose convex surface ofaspherical shape is kept toward the object. The lens unit G22 iscomposed of a biconcave lens L10 whose concave surface of asphericalshape is kept toward the wafer. The lens unit G23 is composed of thefollowing components in order of passage of rays: a planoconvex lens L11whose plane of aspherical shape is kept toward the object; a negativemeniscus lens L12 whose convex surface is kept toward the object; abiconvex lens L13; a positive meniscus lens L14 whose convex surface iskept toward the object; and a biconvex lens L15.

The lens unit G24 is composed of: a biconvex lens L16; a positivemeniscus lens L17 whose convex surface is kept toward the object; apositive meniscus lens L18 whose concave surface of aspherical shape iskept toward the wafer; a positive meniscus lens L19 whose concavesurface of aspherical shape is kept toward the wafer; and a planoconvexlens L20 whose convex surface is kept toward the object.

The catadioptric projection optical system PL1 is constructed to satisfythe condition of 0.2<Mb/L<0.7, where M is a distance on the optical axisAX1 between the reflecting mirror M3 and the aperture stop AS1, and Lthe distance between the reticle R1 and the wafer. When Mb/L is smallerthan the lower limit, it becomes difficult to place and keep the lensesL5-L15 constituting the lens units G21-G23 indispensable for correctionfor various aberrations, particularly, coma, at their accuratepositions. Namely, when Mb/L satisfies the lower limit, it is feasibleto avoid mechanical interference of the concave reflecting mirror M3with the lens units G21-G23. When Mb/L satisfies the upper limit, it isfeasible to avoid an increase in the total length and an increase in thesize of the catadioptric projection optical system PL1. For moreaccurately place and keep each lens L5-L15 and securely avoiding theincrease in the total length of the catadioptric projection opticalsystem PL1, the projection optical system is more preferably constructedto satisfy the condition of 0.25<Mb/L<0.6.

In this fifth example the first intermediate image is formed between thereflecting mirror M3 and the reflecting mirror M4, but the firstintermediate image may be formed in any optical path between thereflecting mirror M2 and the reflecting mirror M4.

Next, the sixth example of the embodiment will be described withreference to the drawing. FIG. 15 is an illustration showing a lensconfiguration of the catadioptric projection optical system according tothe sixth example of the embodiment. The catadioptric projection opticalsystem PL2 of the sixth example is comprised of the following opticalsystems in order from the object side (i.e., the reticle R2 side): afirst imaging optical system G3 for forming a first intermediate imageand a second intermediate image of the reticle R2 located on the firstsurface; and a second imaging optical system G4 for relaying the secondintermediate image of the reticle R2 onto a wafer (not shown) located onthe second surface.

The first imaging optical system G3 is composed of a lens unit with apositive refracting power (field lens unit) G31, after-described lensL25, and six reflecting mirrors M11-M16. The lens unit G31 functions tocorrect for distortion and others and to make the optical systemtelecentric on the reticle R2 side. The lens unit G31 functions to keepthe size of the image of the reticle R2 unchanged even if the reticle R2is placed with deviation from the desired position in the optical-axisdirection; therefore, the performance of the catadioptric projectionoptical system PL2 can be maintained high.

The second imaging optical system G4 is entirely composed oftransmitting optical elements and is composed of a lens unit with apositive refracting power (first lens unit) G41, a lens unit with anegative refracting power (second lens unit) G42, a lens unit with apositive refracting power (third lens unit) G43, an aperture stop AS2,and a lens unit with a positive refracting power (fourth lens unit) G44.The second imaging optical system G4 is free of the optical pathseparation load because it is entirely composed of the transmittingoptical elements; therefore, the image-side numerical aperture of thecatadioptric projection optical system PL2 can be set large and areduced image can be formed at a high reduction rate on the waferlocated on the second surface. The lens units G41-G44 advantageouslyfunction for satisfying the Petzval's condition. The configuration ofthe lens units G41-G44 effectively avoids an increase in the totallength of the catadioptric projection optical system PL2. The lens unitsG41-G43 can correct for various aberrations such as coma.

Here the lens unit G31 is composed of the following components in orderof passage of rays from the object side (reticle R2 side): aplane-parallel plate L21; a positive meniscus lens L22 whose concavesurface of aspherical shape is kept toward the object; a biconvex lensL23; and a biconvex lens L24. The beam transmitted by the biconvex lensL24 passes through the negative meniscus lens (negative lens) L25 withthe concave surface kept toward the object, is reflected by the concavereflecting mirror M11 with the concave surface of aspherical shape kepttoward the object, and passes again through the negative meniscus lensL25. The beam transmitted by the negative meniscus lens L25 is reflectedby the convex reflecting mirror M12 with the convex surface ofaspherical shape kept toward the wafer, to form the first intermediateimage. The beam reflected by the reflecting mirror M12 is reflected bythe concave reflecting mirror M13 with the concave surface kept towardthe object, the convex reflecting mirror M14 with the convex surfacekept toward the wafer, the concave reflecting mirror M15 with theconcave surface of aspherical shape kept toward the object, and theconcave reflecting mirror M16 with the concave surface kept toward thewafer. By adjusting the negative meniscus lens L25, it is feasible toreadily correct for chromatic aberration and to readily satisfy thePetzval's condition. By changing the radius of curvature of eachreflecting mirror M11-M16, it is feasible to readily correct forcurvature of field. The beam reflected by the reflecting mirror M16forms the second intermediate image.

In this case, the concave reflecting mirror M13 is placed at theposition most distant from the optical axis AX2, and the beam can befocused by this concave reflecting mirror M13; therefore, the beam canbe set largely apart from the optical axis AX2 of the catadioptricprojection optical system PL2, without intervention of any lens betweenthe four reflecting mirrors M13-M16, and it is feasible to avoidinterference between beams. By continuously reflecting the beam by thefour reflecting mirrors M13-M16, it is feasible to avoid an increase inthe total length of the catadioptric projection optical system PL2.

The lens unit G41 is composed of the following components in order ofpassage of rays: a positive meniscus lens L26 whose convex surface iskept toward the object; a positive meniscus lens L27 whose concavesurface of aspherical shape is kept toward the wafer; a positivemeniscus lens L28 whose convex surface is kept toward the object; apositive meniscus lens L29 whose concave surface of aspherical shape iskept toward the wafer; and a negative meniscus lens L30 whose convexsurface is kept toward the object.

The lens unit G42 is composed of a biconcave lens L31 formed in theaspherical shape on the wafer side. The lens unit G43 is composed of thefollowing components in order of passage of rays: a biconvex lens L32formed in the aspherical shape on the object side; a negative meniscuslens L33 whose convex surface is kept toward the object; a biconvex lensL34; a biconvex lens L35; and a biconvex lens L36. The lens unit G44 iscomposed of a biconvex lens L37; a positive meniscus lens L38 whoseconvex surface is kept toward the object; a positive meniscus lens L39whose concave surface of aspherical shape is kept toward the wafer; apositive meniscus lens L40 whose concave surface of aspherical shape iskept toward the wafer; and a planoconvex lens L41 whose convex surfaceis kept toward the object.

The catadioptric projection optical system PL2 is constructed to satisfythe condition of 0.2<M2b/L2<0.7, where M2b is a distance on the opticalaxis AX2 between the reflecting mirror M13 and the aperture stop AS2,and L2 the distance between the reticle R2 and the wafer. When M2b/L2 issmaller than the lower limit, it becomes difficult to place and keepeach of the lenses L26-L36 constituting the lens units G41-G43indispensable for correction for various aberrations, particularly,coma, at an accurate position. Namely, when M2b/L2 satisfies the lowerlimit, it is feasible to avoid mechanical interference of the concavereflecting mirror M13 with the lens units G41-G43. When M2b/L2 satisfiesthe upper limit, it is feasible to avoid an increase in the total lengthand an increase in the size of the catadioptric projection opticalsystem PL2. For placing and keeping each lens L26-L36 at a more accurateposition and securely avoiding the increase in the total length of thecatadioptric projection optical system PL2, the optical system is morepreferably constructed to satisfy the condition of 0.25<M2b/L2<0.6.

In the sixth example, the first intermediate image is formed between thereflecting mirror M12 and the reflecting mirror M13, but the firstintermediate image may be formed in any optical path between thereflecting mirror M12 and the reflecting mirror M14.

Next, the seventh example of the embodiment will be described withreference to the drawing. FIG. 16 is an illustration showing a lensconfiguration of the catadioptric projection optical system according tothe seventh example of the embodiment. The catadioptric projectionoptical system PL3 of the seventh example is comprised of the followingoptical systems in order from the object side (i.e., the reticle R3side): a first imaging optical system G5 for forming a firstintermediate image and a second intermediate image of the reticle R3located on the first surface; and a second imaging optical system G6 forrelaying the second intermediate image of the reticle R3 onto a wafer(not shown) located on the second surface.

The first imaging optical system G5 is composed of a lens unit with apositive refracting power (field lens unit) G51, and after-described sixreflecting mirrors M21-M26. The lens unit G51 functions to correct fordistortion and others and to make the optical system telecentric on thereticle R2 side. The lens unit G51 functions to keep the size of theimage of the reticle R3 unchanged even if the reticle R3 is placed withdeviation from the desired position in the direction of the optical-axisAX3; therefore, the performance of the catadioptric projection opticalsystem PL3 can be maintained high.

The second imaging optical system G6 is entirely composed oftransmitting optical elements, and is composed of a lens unit with apositive refracting power (first lens unit) G61; a lens unit with anegative refracting power (second lens unit) G62; a lens unit with apositive refracting power (third lens unit) G63; an aperture stop AS3;and a lens unit with a positive refracting power (fourth lens unit) G64.Since the second imaging optical system G6 is entirely constructed ofthe transmitting optical elements, it is free of the optical pathseparation load; therefore, the image-side numerical aperture of thecatadioptric projection optical system PL3 can be set large and areduced image can be formed at a high reduction rate on the waferlocated on the second surface. The lens units G61-G64 advantageouslyfunction for satisfying the Petzval's condition. The configuration ofthe lens units G61-G64 effectively avoids an increase in the totallength of the catadioptric projection optical system PL3. The lens unitsG61-G63 can correct for various aberrations such as coma.

Here the lens unit G51 is composed of the following components in orderof passage of rays from the object side (reticle R3 side): aplane-parallel plate L51; a positive meniscus lens L52 whose concavesurface of aspherical shape is kept toward the object; a biconvex lensL53; and a biconvex lens L54. The beam transmitted by the biconvex lensL54 is reflected by the concave reflecting mirror M21 with the concavesurface of aspherical shape kept toward the object, the convexreflecting mirror M22 with the convex surface of aspherical shape kepttoward the wafer, and the concave reflecting mirror M23 with the concavesurface kept toward the object, to form the first intermediate image.The beam reflected by the reflecting mirror M23 is reflected by theconvex reflecting mirror M24 with the convex surface kept toward thewafer, the convex reflecting mirror M25 with the convex surface ofaspherical shape kept toward the object, and the concave reflectingmirror M26 with the concave surface kept toward the wafer.

Since the beam is continuously reflected by the reflecting mirrorsM21-M26 without intervention of any lens, it is feasible to readilysatisfy the Petzval's condition through adjustment of each reflectingmirror M21-M26. In addition, a region for holding each reflecting mirrorM21-M26 can be secured, and the curvature of field can be readilycorrected for by changing the radius of curvature of each reflectingmirror M21-M26. The beam reflected by the reflecting mirror M26 formsthe second intermediate image.

In this case, the concave reflecting mirror M23 is located at theposition most distant from the optical axis AX3, and the beam can befocused by this concave reflecting mirror M23; therefore, the beam canbe set largely apart from the optical axis AX3 of the catadioptricprojection optical system PL3, without intervention of any lens betweenthe reflecting mirrors M21-M26, and it is feasible to avoid interferencebetween beams. Since the beam is continuously reflected by the fourreflecting mirrors M23-M26, it is feasible to avoid an increase in thetotal length of the catadioptric projection optical system PL3.

The lens unit G61 is composed of the following components in order ofpassage of rays: a biconvex lens L55; a positive meniscus lens L56 whoseconcave surface of aspherical shape is kept toward the wafer; a positivemeniscus lens L57 whose convex surface is kept toward the object; anegative meniscus lens L58 whose convex surface is kept toward theobject; and a negative meniscus lens L59 whose convex surface ofaspherical shape is kept toward the object. The lens unit G62 iscomposed of a biconcave lens L60 whose concave surface of asphericalshape is kept toward the wafer. The lens unit G63 is composed of thefollowing components in order of passage of rays: a biconvex lens L61whose convex surface of aspherical shape is kept toward the object; anegative meniscus lens L62 whose convex surface is kept toward theobject; a biconvex lens L63; a biconvex lens L64; and a positivemeniscus lens L65 whose concave surface is kept toward the object.

The lens unit G64 is composed of the following components in order ofpassage of rays: a biconvex lens L66; a positive meniscus lens L67 whoseconvex surface is kept toward the object; a positive meniscus lens L68whose concave surface of aspherical shape is kept toward the wafer; apositive meniscus lens L69 whose concave surface of aspherical shape iskept toward the wafer; and a planoconvex lens L70 whose convex surfaceis kept toward the object.

The catadioptric projection optical system PL3 is constructed to satisfythe condition of 0.2<M3/L3<0.7, where M3 is a distance on the opticalaxis AX3 between the reflecting mirror M23 and the aperture stop AS3,and L3 the distance between the reticle R3 and the wafer. When M3/L3 issmaller than the lower limit, it becomes difficult to place and keepeach of the lenses L55-L65 constituting the lens units G61-G63indispensable for correction for various aberrations, particularly,coma, at an accurate position. Namely, when M3/L3 satisfies the lowerlimit, it is feasible to avoid mechanical interference of the concavereflecting mirror M23 with the lens units G61-G63. When M3/L3 satisfiesthe upper limit, it is feasible to avoid an increase in the total lengthand an increase in the size of the catadioptric projection opticalsystem PL3. For placing and keeping each lens L55-L70 at a more accurateposition and securely avoiding the increase in the total length of thecatadioptric projection optical system PL3, the optical system is morepreferably constructed to satisfy the condition of 0.25<M3/L3<0.6.

In this seventh example, the first intermediate image is formed betweenthe reflecting mirror M23 and the reflecting mirror M24, but the firstintermediate image may be formed in any optical path between thereflecting mirror M22 and the reflecting mirror M24.

In application of the catadioptric projection optical systems PL1-PL3 ofthe fifth to seventh examples to the exposure apparatus, pure water(deionized water) with the refractive index of about 1.4 is interposedin the optical path between the planoconvex lens L20, L41, or L70 andthe wafer, where the refractive index of the atmosphere in thecatadioptric projection optical system PL1-PL3 is 1. Therefore, thewavelength of the exposure light in pure water is about 0.71 (1/1.4)times that in the atmosphere, whereby the resolution can be enhanced.

The optical axis AX1-AX3 of every optical element included in thecatadioptric projection optical system PL1-PL3 and having thepredetermined refracting power is arranged substantially on the singlestraight line, and the region of the image formed on the wafer by thecatadioptric projection optical system PL1-PL3 is the off-axis regionnot including the optical axis AX1-AX3. Therefore, it is feasible toreduce the degree of difficulty of production in production of thecatadioptric projection optical system PL1-PL3 and to readily achieverelative adjustment of each optical element.

Since the catadioptric projection optical system PL1-PL3 according tothe fifth to the seventh examples includes the six reflecting mirrorsM1-M6, M11-M16, M21-M26, it is feasible to readily and securely achievethe optical path separation between the beam toward the reticle R1-R3and the beam toward the wafer, without an increase in the total lengthof the catadioptric projection optical system PL1-PL3, even in the casewhere the reticle R1-R3-side and wafer-side numerical apertures of thecatadioptric projection optical system PL1-PL3 are increased in order toenhance the resolution.

The catadioptric projection optical system PL1-PL3 according to thefifth to seventh examples is a thrice-imaging optical system for formingthe first intermediate image and the second intermediate image, in whichthe first intermediate image is an inverted image of the reticle R1-R3,the second intermediate image is an erect image of the reticle R1-R3,and the image formed on the wafer is an inverted image. Therefore, inthe case where the catadioptric projection optical system PL1-PL3 ismounted on the exposure apparatus and where the exposure is carried outwith scanning of the reticle R1-R3 and the wafer, the scanning directionof the reticle R1-R3 can be opposite to that of the wafer, and it isfeasible to readily achieve such adjustment as to decrease a change inthe center of gravity of the entire exposure apparatus. It is alsofeasible to reduce vibration of the catadioptric projection opticalsystem PL1-PL3 due to the change in the center of gravity of the entireexposure apparatus and to achieve good imaging performance throughoutthe entire region in the exposure area.

In the catadioptric projection optical system PL1, PL3 of each of theabove examples, pure water (deionized water) is interposed between thelens located nearest to the wafer, and the wafer, but another mediumhaving the refractive index larger than 1.1 may be interposed, where therefractive index of the atmosphere in the catadioptric projectionoptical system PL1-PL3 is 1.

Next, values of specifications of the catadioptric projection opticalsystem PL1 according to the fifth example shown in FIG. 14 will bepresented. In the specifications, as shown in FIG. 11 described above, Arepresents a radius of a portion where the exposure light is blocked bythe optical elements constituting the catadioptric projection opticalsystem PL1, with the center on the optical axis AX1 of the catadioptricprojection optical system PL1, B a radius of the maximum image heightwith the center on the optical axis AX1 of the catadioptric projectionoptical system PL1, H a length along the Y-direction of the effectiveexposure region, and C a length along the X-direction of the effectiveexposure region. In the specifications, NA indicates the numericalaperture, d the surface separation, n the refractive index, and λ thecenter wavelength. Furthermore, in the specifications, M indicates thedistance on the optical axis AX1 between the concave reflecting mirrorM3 and the unrepresented wafer, and L the distance between the reticleR1 and the wafer.

Table 7 presents the specifications of the optical members of thecatadioptric projection optical system PL1 according to the fifthexample. In the specifications of the optical members of Table 7, eachsurface number in the first column is an order of a surface along thetraveling direction of rays from the object side, the second column aradius of curvature of each surface (mm), the third column an on-axisspacing or surface separation (mm) of each surface, and the fourthcolumn a glass material of each optical member.

Table 8 presents the aspherical coefficients of the lenses with the lenssurface of aspherical shape and the reflecting mirrors used in thecatadioptric projection optical system PL1 according to the fifthexample. In the aspherical coefficients of Table 8, aspherical surfacenumbers in the first column correspond to the surface numbers in thespecifications of the optical members of Table 7. The second columnrepresents the curvature of each aspherical surface (1/mm), the thirdcolumn the conical coefficient k and the 12th-order asphericalcoefficient, the fourth column the 4th-order and 14th-order asphericalcoefficients, the fifth column the 6th-order and 16th-order asphericalcoefficients, the sixth column the 8th-order and 18th-order asphericalcoefficients, and the seventh column the 10th-order and 20th-orderaspherical coefficients.

In the fifth to seventh examples, each aspherical surface is expressedby Eq (a) described above.

Fifth Example Specifications

Image-side NA: 1.20

Exposure area: A=14 mm B=18 mm

-   -   H=26.0 mm C=4 mm

Imaging magnification: ¼

Center wavelength: 193.306 nm

Refractive index of silica: 1.5603261

Refractive index of fluorite: 1.5014548

Refractive index of liquid 1: 1.43664

Dispersion of silica (dn/dλ): −1.591×10⁻⁶/pm

Dispersion of fluorite (dn/dλ): −0.980×10⁻⁶/pm

Dispersion of pure water (deionized water) (dn/dλ): −2.6×10⁻⁶/pm

Values corresponding to Condition Mb=524.49 mm L=1400 mm

TABLE 7 (Specifications of Optical Members) #2 #3 #15 #1 ∞ 45.0000  1: ∞8.0000 #5  2: ∞ 9.4878  3: ASP1 25.3802 #5  4: −244.04741 1.9583  5:2654.01531 49.2092 #5  6: −159.85154 1.1545  7: 294.54453 34.3095 #5  8:−572.08259 156.2051  9: ASP2 −136.2051 #6 10: ASP3 412.6346 #6 11:−418.20026 −205.0204 #6 12: −604.04130 160.2153 #6 13: ASP4 −211.6245 #614: 320.60531 226.6245 15: 224.13260 25.2194 #5 16: 346.75878 1.0000 17:215.47954 34.3600 #5 18: ASP5 1.0000 19: 266.87857 19.9995 #5 20:329.19442 1.0000 21: 196.43240 20.0000 #5 22: 115.87410 6.4756 23: ASP639.3045 #5 24: 99.87482 55.9109 25: −412.64757 24.7282 #5 26: ASP794.8545 27: ASP8 57.3966 #5 28: −227.16104 1.0000 29: 504.83819 20.0000#6 30: 407.86902 12.3535 31: 595.98854 43.0398 #5 32: −2001.40538 1.0000#8 33: 711.19871 32.6046 #5 34: 8598.79354 32.0466 35: 36209.9314130.0000 #5 36: −1731.78793 1.0000 37: ∞ 12.6069 #7 38: 503.84491 53.3626#5 39: −1088.61181 1.0000 40: 192.53858 61.7603 #5 41: 521.19424 1.000042: 122.79200 59.8433 #5 43: ASP9 1.0000 44: 79.97315 39.6326 #14 45:ASP10 1.0000 46: 84.68828 36.1715 #14 47: ∞ 1.0000 #8 #9 ∞ 0.0000 #1:1st surface #2: Radius of curvature (mm) #3: Surface spacing (mm) #5:silica glass #6: reflecting mirror #7: aperture stop #8: pure water #9:2nd surface #14: Fluorite #15: Name of glass material

TABLE 8 (Aspherical Coefficients) k c4 c6 c8 c10 #12 #13 c12 c14 c16 c18c20 ASP1 −0.00059023 0.00000E+00 −2.87641E−08 −1.70437E−11 2.46285E−15−2.74317E−19 2.07022E−23 −7.79530E−28 0.00000E+00 0.00000E+000.00000E+00 ASP2 −0.00205780 0.00000E+00 2.50612E−09 2.95240E−144.37607E−18 −5.55238E−22 3.88749E−26 −1.13016E−30 0.00000E+000.00000E+00 0.00000E+00 ASP3 −0.00058562 0.00000E+00 −6.92554E−091.39659E−13 −1.09871E−18 3.37519E−23 −1.45573E−27 2.27951E−320.00000E+00 0.00000E+00 0.00000E+00 ASP4 −0.00123249 0.00000E+001.93713E−09 1.07185E−12 −3.34552E−16 3.54315E−20 −5.95219E−243.41899E−28 0.00000E+00 0.00000E+00 0.00000E+00 ASP5 0.000201890.00000E+00 1.37544E−07 −1.06394E−11 7.70843E−17 4.90298E−20−3.23126E−24 6.76814E−29 0.00000E+00 0.00000E+00 0.00000E+00 ASP60.00588235 0.00000E+00 2.41559E−07 −1.03766E−11 −6.75114E−17 1.11214E−19−9.45408E−24 3.57981E−28 0.00000E+00 0.00000E+00 0.00000E+00 ASP70.00664255 0.00000E+00 2.62150E−08 −9.25480E−12 −1.77845E−16 5.60675E−20−2.81549E−24 6.89450E−30 0.00000E+00 0.00000E+00 0.00000E+00 ASP80.00000000 0.00000E+00 −1.26430E−08 1.64939E−13 −6.24373E−18 2.07576E−22−5.07100E−27 1.49848E−31 0.00000E+00 0.00000E+00 0.00000E+00 ASP90.00345726 0.00000E+00 5.92282E−08 −1.56640E−12 1.38582E−16 −4.07966E−211.49819E−25 1.10869E−30 0.00000E+00 0.00000E+00 0.00000E+00 ASP100.01038095 0.00000E+00 2.42802E−07 4.29662E−11 1.62230E−15 6.50272E−193.23667E−22 −9.21777E−26 0.00000E+00 0.00000E+00 0.00000E+00 #12:Aspherical surface number #13: Curvature

FIG. 17 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system PL1 according to the presentexample. In FIG. 17, Y indicates the image height, each dashed line thetransverse aberration at the wavelength of 193.3063 nm, each solid linethe transverse aberration at the wavelength of 193.3060 nm, and eachchain line the transverse aberration at the wavelength of 193.3057 nm.As shown in the transverse aberration diagram of FIG. 17, thecatadioptric projection optical system PL1 of the present example hasthe large numerical aperture and is corrected in a good balance foraberration throughout the entire exposure area though it has no largeoptical element.

Next, the specifications of the catadioptric projection optical systemPL2 according to the sixth example shown in FIG. 15 will be presented.Table 9 presents the specifications of the optical members of thecatadioptric projection optical system PL2 according to the sixthexample. Table 10 presents the aspherical coefficients of the lenseswith the lens surface of aspherical shape and the reflecting mirrorsused in the catadioptric projection optical system PL2 according to thesixth example. In the specifications, the specifications of the opticalmembers, and the aspherical coefficients, the description will be givenusing the same symbols as those in the description of the catadioptricprojection optical system PL1 according to the fifth example.

Sixth Example Specifications

Image-side NA: 1.20

Exposure area: A=13 mm B=17 mm

-   -   H=26.0 mm C=4 mm

Imaging magnification: ¼

Center wavelength: 193.306 nm

Refractive index of silica: 1.5603261

Refractive index of fluorite: 1.5014548

Refractive index of liquid 1: 1.43664

Dispersion of silica (dn/dλ): −1.591×10⁻⁶/pm

Dispersion of fluorite (dn/dλ): −0.980×10⁻⁶/pm

Dispersion of pure water (deionized water) (dn/dλ): −2.6×10⁻⁶/pm

Values corresponding to Condition Mb=482.14 mm L=1400 mm

TABLE 9 (Specifications of Optical Members) #2 #3 #15 #1 ∞ 50.9535  1: ∞8.0000 #5  2: ∞ 12.7478  3: ASP1 32.5506 #5  4: −184.43053 1.0000  5:532.87681 45.9762 #5  6: −271.53626 1.3173  7: 374.46315 38.0103 #5  8:−361.42951 147.1771  9: −380.08052 20.0000 #5 10: −594.49774 5.5356 11:ASP2 −5.5356 #6 12: −594.49774 −20.0000 #5 13: −389.08052 −127.0301 14:ASP3 430.8932 #6 15: −450.43913 −215.6393 #6 16: −704.67689 163.6052 #617: ASP4 −206.3833 #6 18: 317.07489 228.3275 #6 19: 248.60032 30.8186 #520: 964.03405 1.0000 21: 170.07823 20.0000 #5 22: ASP5 1.0778 23:174.13726 29.8902 #5 24: 294.93424 1.0798 25: 160.77849 33.1276 #5 26:ASP6 9.4275 27: 1185.57325 20.0000 #5 28: 103.90360 46.9708 29:−676.67026 24.5184 #5 30: ASP7 83.5410 31: ASP8 47.4275 #5 32:−317.19307 1.0000 33: 688.27957 20.0000 #5 34: 513.64357 11.2866 35:883.25368 40.1774 #5 36: −959.41738 1.0000 #8 37: 1222.93397 34.5841 #538: −1403.11949 16.9031 39: 2169.40706 37.3055 #5 40: −889.78387 1.000041: ∞ 9.8461 #7 42: 458.32781 52.3568 #5 43: −1741.66958 1.0000 44:215.86566 59.3939 #5 45: 659.70674 1.0000 46: 134.64784 58.8510 #5 47:ASP9 1.0004 48: 96.99608 49.9011 #5 49: ASP10 1.0194 50: 80.2224540.8996 #5 51: ∞ 1.0000 #9 ∞ #1: 1st surface #2: Radius of curvature(mm) #3: Surface spacing (mm) #5: silica glass #6: reflecting mirror #7:aperture stop #8: pure water #9: 2nd surface #14: Fluorite #15: Name ofglass material

TABLE 10 (Aspherical Coefficients) k c4 c6 c8 c10 #12 #13 c12 c14 c16c18 c20 ASP1 −0.00057910 0.00000E+00 −9.03366E−08 3.28394E−12−4.06402E−16 2.52900E−20 −9.19294E−25 2.02082E−30 0.00000E+000.00000E+00 0.00000E+00 ASP2 −0.00243076 0.00000E+00 3.35076E−092.88286E−14 8.73468E−18 −7.00411E−22 4.21327E−26 −9.88714E−310.00000E+00 0.00000E+00 0.00000E+00 ASP3 −0.00032257 0.00000E+00−6.53400E−09 1.15038E−13 −9.61655E−19 8.51651E−23 −3.17817E−274.60017E−32 0.00000E+00 0.00000E+00 0.00000E+00 ASP4 −0.000585010.00000E+00 2.54270E−09 0.81523E−13 −1.08474E−16 0.27615E−21−7.45415E−25 6.45741E−29 0.00000E+00 0.00000E+00 0.00000E+00 ASP50.00574270 0.00000E+00 2.69000E−08 −1.93073E−12 −2.23058E−16 2.03519E−20−2.27002E−24 8.48621E−29 0.00000E+00 0.00000E+00 0.00000E+00 ASP60.00281530 0.00000E+00 −7.99356E−08 1.14147E−11 −4.87397E−16 8.76022E−20−3.55808E−24 1.84260E−28 0.00000E+00 0.00000E+00 0.00000E+00 ASP70.00667798 0.00000E+00 −1.01256E−08 −5.60515E−12 −6.85243E−172.18957E−20 −1.24639E−24 −1.61382E−29 0.00000E+00 0.00000E+000.00000E+00 ASP8 0.00000970 0.00000E+00 −1.68383E−08 1.90215E−13−8.11478E−18 3.37339E−22 −1.15048E−26 5.21646E−31 0.00000E+000.00000E+00 0.00000E+00 ASP9 0.00313892 0.00000E+00 4.21089E−08−8.07510E−13 5.31944E−17 −4.15094E−22 −5.28946E−27 1.60853E−300.00000E+00 0.00000E+00 0.00000E+00 ASP10 0.00959788 0.00000E+002.16924E−07 3.52791E−11 1.11831E−15 1.12987E−18 −4.81835E−23 1.62262E−260.00000E+00 0.00000E+00 0.00000E+00 #12: Aspherical surface number #13:Curvature

FIG. 18 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system PL2 according to the presentexample. In FIG. 18, Y indicates the image height, each dashed line thewavelength of 193.3063 nm, each solid line the wavelength of 193.3060nm, and each chain line the wavelength of 193.3057 nm. As shown in thetransverse aberration diagram of FIG. 18, the catadioptric projectionoptical system PL2 of the present example has the large numericalaperture and is corrected in a good balance for aberration throughoutthe entire exposure area though it has no large optical element.

Next, the specifications of the catadioptric projection optical systemPL3 according to the seventh example shown in FIG. 16 will be presented.Table 11 presents the specifications of the optical members of thecatadioptric projection optical system PL3 according to the seventhexample. Table 12 presents the aspherical coefficients of the lenseswith the lens surface of aspherical shape and the reflecting mirrorsused in the catadioptric projection optical system PL3 according to theseventh example. In the specifications, the specifications of theoptical members, and the aspherical coefficients, the description willbe given using the same symbols as those in the description of thecatadioptric projection optical system PL1 according to the fifthexample.

Seventh Example Specifications

Image-side NA: 1.20

Exposure area: A=13 mm B=17 mm

-   -   H=26.0 mm C=4 mm

Imaging magnification: ⅕

Center wavelength: 193.306 nm

Refractive index of silica: 1.5603261

Refractive index of fluorite: 1.5014548

Refractive index of liquid 1: 1.43664

Dispersion of silica (dn/dλ): −1.591×10⁻⁶/pm

Dispersion of fluorite (dn/dλ): −0.980×10⁻⁶/pm

Dispersion of pure water (deionized water) (dn/dλ): −2.6×10⁻⁶/pm

Condition Mb=508.86 mm L=1400 mm

TABLE 11 (Specifications of Optical Members) #2 #3 #15 #1 ∞ 63.0159  1:∞ 8.0000 #5  2: ∞ 11.6805  3: ASP1 30.7011 #5  4: −244.82575 1.0000  5:520.72375 50.6283 #5  6: −283.00136 1.0000  7: 455.76731 37.0794 #5  8:−509.23840 143.7025  9: ASP2 −123.7025 #6 10: ASP3 394.2980 #6 11:−398.57468 −201.7192 #6 12: −485.11237 157.8027 #6 13: ASP4 −206.6789 #614: 329.37813 221.6789 #6 15: 411.95851 28.1592 #5 16: −3890.383871.1778 17: 141.65647 33.4870 #5 18: ASP5 1.0000 19: 216.09570 28.6534 #520: 461.77835 1.0000 21: 202.12479 20.2182 #5 22: 117.79321 2.6054 23:ASP6 20.0000 #5 24: 98.31887 51.9992 25: −251.39135 35.2622 #5 26: ASP789.1855 27: ASP8 42.0591 #5 28: −303.33648 2.1164 29: 606.18864 28.5148#5 30: 488.85229 11.9006 31: 811.09260 45.2273 #5 32: −813.38538 1.000033: 1012.41934 42.1336 #5 34: −973.64830 21.5611 35: −32382.9741029.5159 #5 36: −1075.05682 1.0000 37: ∞ 6.3302 #7 38: 371.59007 56.0505#5 39: −4689.87645 9.3746 40: 204.82419 53.7618 #5 41: 494.59116 1.000042: 125.95227 57.4813 #5 43: ASP9 1.0101 44: 92.58526 43.4772 #5 45:ASP10 1.0360 46: 85.28679 42.2466 #5 47: ∞ 1.0000 #8 #9 ∞ #1: 1stsurface #2: Radius of curvature (mm) #3: Surface spacing (mm) #5: silicaglass #6: reflecting mirror #7: aperture stop #8: pure water #9: 2ndsurface #14: Fluorite #15: Name of glass material

TABLE 12 (Aspherical Coefficients) k c4 c6 c8 c10 #12 #13 c12 c14 c16c18 c20 ASP1 −0.0004476 0.00000E+00 −6.28600E−08 2.01003E−12−1.86171E−16 4.72866E−21 4.25382E−26 −8.36739E−30 0.00000E+000.00000E+00 0.00000E+00 ASP2 −0.0019308 0.00000E+00 5.30847E−092.32487E−13 −9.96057E−18 1.35214E−21 −9.28498E−26 2.73795E−300.00000E+00 0.00000E+00 0.00000E+00 ASP3 0.0000635 0.00000E+00−1.46917E−08 2.39879E−13 1.88016E−18 −1.08670E−22 1.55922E−27−1.05341E−32 0.00000E+00 0.00000E+00 0.00000E+00 ASP4 −0.00097420.00000E+00 2.25661E−09 8.15504E−13 −1.75777E−16 1.04720E−20−2.44697E−24 2.57932E−28 0.00000E+00 0.00000E+00 0.00000E+00 ASP50.0045455 0.00000E+00 7.76937E−08 −8.42991E−12 3.25677E−16 8.77802E−23−2.71916E−25 −2.25230E−30 0.00000E+00 0.00000E+00 0.00000E+00 ASP60.0078125 0.00000E+00 1.83201E−07 −2.17156E−11 1.87637E−15 −2.53394E−191.70711E−23 −1.55669E−27 0.00000E+00 0.00000E+00 0.00000E+00 ASP70.0063619 0.00000E+00 3.50299E−09 −5.60629E−12 −2.85922E−18 2.57458E−20−2.26908E−24 3.14291E−29 0.00000E+00 0.00000E+00 0.00000E+00 ASP80.0001516 0.00000E+00 −1.73728E−08 2.07225E−13 −7.68040E−18 2.99860E−22−9.28797E−27 3.18623E−31 0.00000E+00 0.00000E+00 0.00000E+00 ASP90.0037449 0.00000E+00 4.54024E−08 −8.98172E−13 6.42893E−17 5.94025E−22−6.11068E−26 4.37709E−30 0.00000E+00 0.00000E+00 0.00000E+00 ASP100.0093466 0.00000E+00 2.17665E−07 2.75156E−11 1.89892E−15 3.45960E−197.23960E−23 −1.19099E−26 0.00000E+00 0.00000E+00 0.00000E+00 #12:Aspherical surface number #13: Curvature

FIG. 19 is a transverse aberration diagram showing the transverseaberration in the meridional direction and in the sagittal direction ofthe catadioptric projection optical system PL3 according to the presentexample. In FIG. 19, Y indicates the image height, each dashed line thewavelength of 193.3063 nm, each solid line the wavelength of 193.3060nm, and each chain line the wavelength of 193.3057 nm. As shown in thetransverse aberration diagram of FIG. 19, the catadioptric projectionoptical system PL3 of the present example has the large numericalaperture and is corrected in a good balance for aberration throughoutthe entire exposure area though it has no large optical element.

The projection optical systems of the respective examples describedabove can be applied each to the projection exposure apparatus shown inFIG. 1. The projection exposure apparatus shown in FIG. 1 is able toincrease the effective numerical aperture on the wafer W side to 1.0 ormore and to enhance the resolution, because pure water with therefractive index of about 1.4 for the exposure light is interposedbetween the projection optical system PL and the wafer W. Since theprojection exposure apparatus shown in FIG. 1 has the projection opticalsystem PL consisting of the catadioptric projection optical systemaccording to each of the aforementioned examples, it is able to readilyand securely achieve the optical path separation between the beam towardthe reticle and the beam toward the wafer in the projection opticalsystem PL, even in the case where the reticle-side and wafer-sidenumerical apertures are increased. Therefore, good imaging performancecan be achieved throughout the entire region in the exposure area and afine pattern can be suitably exposed.

Since the projection exposure apparatus shown in FIG. 1 uses the ArFexcimer laser light as the exposure light, pure water is supplied as theliquid for liquid immersion exposure. Pure water is easily available inlarge quantity in semiconductor manufacturing facilities and others andhas the advantage of no adverse effect on the photoresist on thesubstrate (wafer) W, the optical elements (lenses), and others. Sincepure water has no adverse effect on environments and contains anextremely low amount of impurities, we can also expect the action ofcleaning the surface of the wafer W and the surface of the opticalelement located on the end surface of the projection optical system PL.

Pure water (water) is said to have the refractive index n of about 1.44for the exposure light of the wavelength of approximately 193 nm. In thecase where the ArF excimer laser light (wavelength 193 nm) is used as alight source of exposure light, the wavelength is reduced to 1/n, i.e.,about 134 nm on the substrate to achieve a high resolution. Furthermore,the depth of focus is increased to about n times or about 1.44 timesthat in air.

The liquid can also be another medium having the refractive index largerthan 1.1 for the exposure light. In this case, the liquid can be anyliquid that is transparent to the exposure light, has the refractiveindex as high as possible, and is stable against the projection opticalsystem PL and the photoresist on the surface of the wafer W.

Where the F₂ laser light is used as the exposure light, the liquid canbe a fluorinated liquid, for example, such as fluorinated oils andperfluorinated polyethers (PFPE), which can transmit the F₂ laser light.

The present invention is also applicable to the exposure apparatus ofthe twin stage type provided with two stages independently movable inthe XY directions while separately carrying their respective substratesto be processed, such as wafers, as disclosed in Japanese PatentApplications Laid-Open No. 10-163099, Laid-Open No. 10-214783,Jp-A-2000-505958, and so on.

When the liquid immersion method is applied as described above, thenumerical aperture (NA) of the projection optical system PL can be 0.9to 1.3. In cases where the numerical aperture (NA) of the projectionoptical system PL is so large as described, use of randomly polarizedlight conventionally applied as the exposure light can degrade theimaging performance by virtue of its polarization effect, and it is thusdesirable to use polarized illumination. A preferred configuration inthose cases is such that linearly polarized illumination is effected inalignment with the longitudinal direction of line patterns ofline-and-space patterns on the reticle (mask) R so that diffracted lightof the s-polarized component (component in the polarization directionalong the longitudinal direction of the line patterns) is more emittedfrom the patterns of the reticle (mask) R. When the liquid fills thespace between the projection optical system PL and the resist applied onthe surface of the wafer W, the transmittance becomes higher on theresist surface for the diffracted light of the s-polarized componentcontributing to improvement in contrast than in the case where air (gas)fills the space between the projection optical system PL and the resistapplied on the surface of the wafer W. For this reason, the high imagingperformance can also be achieved even in the case where the numericalaperture (NA) of the projection optical system PL exceeds 1.0. It ismore effective to use the phase shift mask, the oblique incidenceillumination method (particularly, the dipole illumination) in alignmentwith the longitudinal direction of line patterns as disclosed inJapanese Patent Application Laid-Open No. 6-188169, etc. properly incombination.

The exposure apparatus of the aforementioned embodiment can producemicrodevices (semiconductor devices, image pickup devices,liquid-crystal display devices, thin-film magnetic heads, etc.) byilluminating the reticle (mask) by the illumination device (illuminationstep) and performing an exposure of a transcription pattern formed onthe mask, onto the photosensitive substrate by the projection opticalsystem (exposure step). An example of a method for producingsemiconductor devices as microdevices by forming a predetermined circuitpattern on a wafer or the like as a photosensitive substrate by use ofthe exposure apparatus of the present embodiment will be described belowwith reference to the flowchart of FIG. 20.

First, step 301 in FIG. 20 is to form an evaporated metal film on eachof wafers in one lot. Next step 302 is to apply a photoresist onto themetal film on each of the wafers in the lot. Thereafter, step 303 is tosequentially perform an exposure to transcribe an image of a pattern ona mask into each shot area on each of the wafers in the lot through theprojection optical system, using the exposure apparatus of the presentembodiment. Step 304 thereafter is to perform development of thephotoresist on each of the wafers in the lot, and next step 305 is toperform etching with the resist pattern as a mask on each of the wafersin the lot to form a circuit pattern corresponding to the pattern on themask, in each shot area on each wafer.

Thereafter, through formation of circuit patterns of upper layers andothers, the devices such as semiconductor devices are produced. Thesemiconductor device production method described above permits us toobtain the semiconductor devices with an extremely fine circuit patternat high throughput. Step 301 to step 305 are to perform the respectivesteps of evaporation of metal on the wafers, application of the resistonto the metal film, exposure, development, and etching, but it isneedless to mention that the method may be so arranged that, prior tothese steps, a silicon oxide film is formed on the wafer and thereafterthe resist is applied onto the silicon oxide film, followed by therespective steps of exposure, development, etching, and so on.

The exposure apparatus of the present embodiment can also produce aliquid-crystal display device as a microdevice by forming predeterminedpatterns (circuit pattern, electrode pattern, etc.) on a plate (glasssubstrate). An example of a method of this production will be describedbelow with reference to the flowchart of FIG. 21. In FIG. 21, patternforming step 401 is to execute a so-called photolithography step ofperforming an exposure to transcribe a pattern of a mask onto aphotosensitive substrate (a glass substrate coated with a resist or thelike) by the exposure apparatus of the present embodiment. Thisphotolithography step results in forming the predetermined patternincluding a number of electrodes and others on the photosensitivesubstrate. Thereafter, the exposed substrate is processed throughrespective steps of development, etching, resist removal, and so on toform a predetermined pattern on the substrate, and is then transferredto next color filter forming step 402.

Next, the color filter forming step 402 is to form a color filter in aconfiguration wherein a number of sets of three dots corresponding to R(Red), G (Green), and B (Blue) are arrayed in a matrix, or in aconfiguration wherein a plurality of sets of filters of three stripes ofR, G, and B are arranged in the direction of horizontal scan lines.After the color filter forming step 402, cell assembly step 403 is thenexecuted. The cell assembly step 403 is to assemble a liquid crystalpanel (liquid crystal cell), using the substrate with the predeterminedpattern obtained in the pattern forming step 401, the color filterobtained in the color filter forming step 402, and so on. In the cellassembly step 403, for example, a liquid crystal is poured into thespace between the substrate with the predetermined pattern obtained inthe pattern forming step 401 and the color filter obtained in the colorfilter forming step 402, thereby producing a liquid crystal panel(liquid crystal cell).

Module assembly step 404 thereafter is to attach each of components suchas an electric circuit, a backlight, etc. for display operation of theassembled liquid crystal panel (liquid crystal cell), thereby completinga liquid-crystal display device. The production method of theliquid-crystal display device described above permits liquid-crystaldisplay devices with the extremely fine circuit pattern to be producedat high throughput.

As described above, the projection optical system according to the firstaspect of the embodiment comprises at least two reflecting mirrors andthe boundary lens with the surface on the first surface side having thepositive refracting power, has all the transmitting members andreflecting members arranged along the single optical axis, and has theeffective imaging area not including the optical axis, wherein theoptical path between the boundary lens and the second surface is filledwith the medium having the refractive index larger than 1.1. As aresult, the embodiment successfully realizes the relatively compactprojection optical system having the excellent imaging performance aswell corrected for various aberrations such as chromatic aberration andcurvature of field and being capable of securing the large effectiveimage-side numerical aperture while well suppressing the reflection losson the optical surfaces.

In the projection optical system according to the second aspect of theembodiment, the intermediate image of the first surface is formed in thefirst imaging optical system, and it is thus feasible to readily andsecurely achieve the optical path separation between the beam toward thefirst surface and the beam toward the second surface, even in the casewhere the numerical apertures of the projection optical system areincreased. Since the second imaging optical system is provided with thefirst lens unit having the negative refracting power, it is feasible toshorten the total length of the catadioptric projection optical systemand to readily achieve the adjustment for satisfying the Petzval'scondition. Furthermore, the first lens unit relieves the variation dueto the difference of field angles of the beam expanded by the firstfield mirror, so as to suppress occurrence of aberration. Therefore,good imaging performance can be achieved throughout the entire region inthe exposure area, even in the case where the object-side and image-sidenumerical apertures of the catadioptric projection optical system areincreased in order to enhance the resolution.

The projection optical system according to the third aspect of theembodiment comprises at least six mirrors, and thus the firstintermediate image and the second intermediate image can be formedwithout increase in the total length of the catadioptric projectionoptical system, even in the case where the object-side and image-sidenumerical apertures of the catadioptric projection optical system areincreased in order to enhance the resolution. Therefore, it is feasibleto readily and securely achieve the optical path separation between thebeam toward the first surface and the beam toward the second surface.Since the projection optical system is provided with at least sixmirrors and the second lens unit having the negative refracting power,the Petzval's condition can be readily met and correction for aberrationcan be readily made, through the adjustment of each mirror or each lensforming the second lens unit, or the like.

The projection optical system according to the third aspect of theembodiment is the thrice-imaging optical system, whereby the firstintermediate image is an inverted image of the first surface, the secondintermediate image an erect image of the first surface, and the imageformed on the second surface an inverted image. Therefore, in the casewhere the catadioptric projection optical system of the embodiment ismounted on the exposure apparatus and where the exposure is carried outwith scanning of the first surface and the second surface, the scanningdirection of the first surface can be made opposite to that of thesecond surface and it is feasible to readily achieve such adjustment asto decrease the change in the center of gravity of the entire exposureapparatus. By reducing the change in the center of gravity of the entireexposure apparatus, it is feasible to reduce the vibration of thecatadioptric projection optical system and to achieve good imagingperformance throughout the entire region in the exposure area.

Accordingly, the exposure apparatus and exposure method using theprojection optical system of the embodiment are able to perform theexposure to transcribe a fine pattern with high precision, through theprojection optical system having the excellent imaging performance andthe large effective image-side numerical aperture, consequently, highresolution. With use of the exposure apparatus equipped with theprojection optical system of the embodiment, it is feasible to producegood microdevices by the high-precision projection exposure through thehigh-resolution projection optical system.

From the invention thus described, it will be obvious that the inventionmay be varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedfor inclusion within the scope of the following claims.

What is claimed is:
 1. An immersion projection optical system whichimages a pattern provided in an object surface of the immersionprojection optical system onto an image surface of the immersionprojection optical system, comprising: a first lens unit including atleast to lenses; a mirror group, arranged between the first lens unitand the image surface, including of two mirrors; a second lens unit,arranged between the mirror group and the image surface, including atleast one lens; a third lens unit, arranged between the second lens unitand the image surface, including at least two negative lenses; and afourth lens unit, arranged between the second lens unit and the imagesurface, including a liquid immersed optical element which is contactwith a liquid and a plurality of lenses between the third lens unit andthe liquid immersed optical element, wherein a maximum diameter of thefourth lens unit larger than a maximum diameter of the third lens unit,wherein number of mirrors belonging the immersion projection opticalsystem are two, and wherein every transmitting member and every mirrorconstituting the projection optical system are arranged along a singlestraight optical axis.
 2. The immersion projection optical systemaccording to claim 1, wherein the immersion projection optical systemincluding an effective imaging area of a predetermined shape notincluding the optical system.
 3. The immersion projection optical systemaccording to claim 1, wherein at least one intermediate image of theobject surface is formed between the first lens unit and the third lensunit.
 4. The immersion projection optical system according to claim 3,wherein the at least one intermediate image is formed in an optical pathbetween the mirror group and the third lens unit.
 5. The immersionprojection optical system according to claim 1, wherein the fourth lensunit including an aperture stop arranged between a plurality of lensesand the liquid immersed optical element.
 6. The immersion projectionoptical system according to claim 1, wherein the two mirrors of themirror group is two concave mirrors.
 7. The immersion projection opticalsystem according to claim 1, wherein the liquid immersed optical elementis a positive lens including a convex surface facing toward the objectsurface.
 8. The immersion projection optical system according to claim7, wherein the fourth lens unit including a meniscus lens adjoining thepositive lens, a concave surface of the meniscus lens facing the convexsurface of the positive lens.
 9. The immersion projection optical systemaccording to claim 1, wherein a diameter of the second lens unit largerthan the diameter of the third lens unit.
 10. The immersion projectionoptical system according to claim 1, wherein the fourth lens unitincluding an aperture stop, and wherein an optically conjugate point ofthe aperture stop is formed between the first lens unit and the secondlens unit.
 11. The immersion projection optical system according toclaim 10, wherein the two mirrors away from an optically conjugate pointof the aperture stop.
 12. The immersion projection optical systemaccording to claim 1, wherein the fourth lens unit including an aperturestop and at least two positive lenses between the aperture stop and theliquid immersed optical element.
 13. The immersion projection opticalsystem according to claim 12, the at least two positive lenses of thefourth lens unit including a positive meniscus lens whose concavesurface facing the liquid immersed lens.
 14. The immersion projectionoptical system according to claim 1, wherein the fourth lens unitincluding an aperture stop and a meniscus lens, arranged between thethird lens unit and the aperture stop, whose concave surface facing thethird lens unit.
 15. The immersion projection optical system accordingto claim 14, wherein the meniscus lens of the fourth lens unit arrangedadjacent to the third lens unit.
 16. The immersion projection opticalsystem according to claim 1, wherein the second lens unit including aplurality of lenses.
 17. The immersion projection optical systemaccording to claim 1, further comprising a lens arranged between the twomirrors of the mirror group.
 18. The immersion projection optical systemaccording to claim 1, number of mirrors of the mirror group is two. 19.A projection-exposure system for use in microlithography including anillumination system and the immersion projection optical systemaccording to claim
 1. 20. A method for fabricating semiconductor devicesor other types of micro devices, comprising: providing a mask having aprescribed pattern; illuminating the mask with ultraviolet light havinga prescribed wavelength; projecting an image of the pattern onto aphotosensitive substrate arranged in the vicinity of the image plane ofthe immersion projection optical system according to of claim 1; andproviding a liquid between the immersion projection optical system andthe photosensitive substrate.